Bullet 1+0
Blitz 5+3
Rapid 10+5
Classical 30+20
Increments are added automatically after each move. Set yours higher than the computer's for a per-move handicap in your favor.
A boost adds time to your own clock only. You get a fresh set of boosts every 10 of your moves; unused ones don't carry over. Switching to Untimed turns the clock off right away.