You can normally get two bonus dice for your action roll (some special abilities might give you additional bonus dice).

For one bonus die, you can get assistance from a teammate. They take 1 stress, say how they help you, and give you +1d.

For another bonus die, you can either push yourself (take 2 stress) or you can accept a Devil's Bargain (you can't get dice for both, it's one or the other).