They are just as simple as any other turn signal: Take two wires connect them to the corresponding wires on your bike. Add a resistor to slow down the blink rate to something more reasonable (optional). Done, next project.
Check your local laws to see what is allowed/disallowed as far as turn signals. I don't think there is anything illegal about mirror signals (i.e. gixxers come stock that way), but I wouldn't trust these things by themselves. They are a nice extra, but aren't quite bright enough to go it alone. Spend the extra 30 bucks to get a good set of LED flashers. At least, that's my opinion.