I'm handy, but not familiar with bicycles so much, and it took me several minutes to figure out how to install my new kickstand properly. In the interest of saving someone else those few minutes, here's how to do it. (Note that some bikes won't have the installation bracket, but these are likely to be a) VERY high end, or b) VERY antique and in either case you probably don't want to add a cheap kickstand anyway.)
The kickstand should come with a bolt and a kind of top bracket, which at first glance seems not to really fit with the stand part. The only tool you'll need is a wrench - my kickstand had a bolt that a 14mm wrench fit well. An adjustable wrench would also work.
The third pic is of the part of the bicycle frame that the kickstand will attach to.
Step 1: Attach the Bolt
This pic shows the order of the parts: above the two lower frame bars, place the second kickstand bracket. Below it, place the main kickstand part. Note that the bracket on the bike may have flanges to keep the kickstand positioned properly (see second pic). If you miss the flanges, your kickstand may interfere with the rear shift cable, which is not advised. It'll sit in easily enough if you know there's a bracket there.
Note also that the top kickstand bracket may want to interfere with the pedal gear shift cable! This is just bad design on my bike, but there's no reason not to simply rotate the bracket to avoid the cable. As long as there's enough bracket on the bar to hold the kickstand, you're fine.
Insert the bolt, from the top, through the top kickstand bracket, through the hole in the bike frame bracket, and into the main kickstand part. Screw it in.
Step 2: Lean Proudly.
And wash your hands, you've got bicycle grease all over them, ew.