Book of Skelos and Core book have rules for sorcery. Just taking the patron and becoming a sorcerer causes the character to loose two points of resolve permanently.
Certain spells also cause a character to loose permanent resolve.
Spending doom is good for a character for rolling a few extra d20s.
Most of the time the sorcerer makes a sorcery test to cast a spell.
They must spend the resolve/gold/vigor costs depending on the type the spell requires and cast the spell taking a minor and standard action.
The spells are not static like dnd spells as you can manage the effects of most spells by spending the amount of momentum you get.
I think somewhere on this forum is a sorcery FAQ.
Edit : Found it here Sorcery FAQ