The stick on strike indicators are very easy to use. You simply peal off a strike indicator and pinch it closed over your line. When you're done, you take them off the line. That's it.
They'll float light nymphs and small bead head flies. Some heavy rigs will sink them. Orange is a good color because you can see it in almost all conditions.
Many people like these indicators because they are very light and easy to cast. Some don't like them because they can leave some sticky residue on the leader. It's a matter of taste and fishing method. But you can find these in every fly shop in America, and that's because they work.
These indicators are also used by some spin fisherman targeting trout and panfish with light presentations. They work for micro fishing too.