Connect the battery to the speed controller and the throttle. Follow the instructions included with the kit to connect each part. Typically, you’ll only need to plug the connector on the speed controller into the connector on the battery, then repeat the process for the throttle. Be sure not to touch the battery wires together, as this could create a dangerous spark! 
In conformance with legislation adopted by the U.S. Congress defining this category of electric-power bicycle (15 U.S.C. 2085(b)), CPSC rules stipulate that low speed electric bicycles (to include two- and three-wheel vehicles) are exempt from classification as motor vehicles providing they have fully operable pedals, an electric motor of less than 750W (1 hp), and a top motor-powered speed of less than 20 miles per hour (32 km/h) when operated by a rider weighing 170 pounds. An electric bike remaining within these specifications is subject to the CPSC consumer product regulations for a bicycle. Commercially manufactured e-bikes exceeding these power and speed limits are regulated by the federal DOT and NHTSA as motor vehicles, and must meet additional safety requirements. The legislation enacting this amendment to the CPSC is also known as HR 727. The text of HR 727 includes the statement: "This section shall supersede any State law or requirement with respect to low-speed electric bicycles to the extent that such State law or requirement is more stringent than the Federal law or requirements." (Note that this refers to consumer product regulations enacted under the Consumer Product Safety Act. Preemption of more stringent state consumer product regulations does not limit State authority to regulate the use of electric bicycles, or bicycles in general, under state vehicle codes.)
If you’ve got the cash and want to get into ebikes, don’t buy this Rattan. My best advice if you have the money is buy a bike store bike with a Bosch/Brose/Yamaha/Shimano drivetrain. We review lots of them here but I’m currently riding a $2000 Raleigh. If you only have around $1,000+ to spend, head to Luna/Rad/Sondors or at least something from a company you’ve heard of with a Bafang motor.
UPDATE (2019-03-15): I've now got more than 110 miles on the bike and still loving it. The longest ride I did was 28.5 miles and the display was still showing about two bars left on the battery. But the battery gauge is not accurate. Even when it went down to two bars it would also jump back up to 4 bars and stay that way for awhile. So it's really hard to tell how much power you have left. On one ride, after 14 miles the pedal assist stopped working all of a sudden. I stopped and re-seated the cadence sensor and it started working again. Even when PAS didn't work the throttle was still working. It hasn't happened since. There was also a lot of rattling noises which I found was the battery rattling around in the mounting bracket.
If you are an experienced rider this is actually annoying as hell. Personally, I tend to leave whatever I'm riding in a high gear all the time, because my body is like a powerful machine, and I found the way it slowed my escape from the lights quite disconcerting. For beginners, it could be useful, but it's worth remembering that the whole point of e-bikes is that the motor helps you along anyway, so I do really question the usefulness of this.
Bicycles helped create, or enhance, new kinds of businesses, such as bicycle messengers, traveling seamstresses, riding academies, and racing rinks. Their board tracks were later adapted to early motorcycle and automobile racing. There were a variety of new inventions, such as spoke tighteners, and specialized lights, socks and shoes, and even cameras, such as the Eastman Company's Poco. Probably the best known and most widely used of these inventions, adopted well beyond cycling, is Charles Bennett's Bike Web, which came to be called the jock strap.
Built around a heavy-duty alloy frame, the GSD eschews many of the traits of other cargo bikes: long wheelbases, bigger wheels, and especially, an unwieldy ride. Yet it boasts an extensive capacity, nimble handling—even fully loaded, thanks to a short wheelbase and 20-inch wheels—and enduring range in a package not much bigger than most non-cargo e-bikes. The stout frame holds a 250-watt Bosch motor that gives up to 275 percent of your power back to the pedals and reaches 20 mph. The GSD has room for two battery packs, extending the batteries’ combined range to a claimed 150 miles and making the Tern one of the longest-lasting e-bikes on the market. A laundry list of accessories and a (claimed) 396-pound carrying capacity round out the GSD’s status as an epic day-tripper.
Perhaps the cleverest thing of all about the Electric Brompton is that despite all the extra stuff, it folds up exactly the same as the non-powered variety. It's so simple, and unlike certain folding bikes we could mention, what you're left with is a genuinely small thing, rather than something that's about the size of a bike with the front wheel taken off.