SteezyJapaneezyGotcha. But the first step is to visit that DMV you were talking about right?
I would call the DMV first and ask them about your international status and your age. As mentioned above, kids generally have to have a learner's permit for 6 months before they can get their license. I believe that's only necessary because they're not 16 yet. For example, if you never got your permit and you're now 20, I think you're allowed to just go try for a license.
This, however, is a question suited for the DMV. Call them first, ask them what to do as an international or as a 20 year old.
They'll tell you one of two things:
1) you still need a permit for X months before you can get a license. In which case you'll have to go in and take the written test for a permit. it's based completely on the content of that pdf I posted. So that's all you need to study.
2) you do not need a permit, you can take your license test whenever. In this case, you'll still have to study and spend some time learning how to drive (although it would be illegal for you to do this without a permit). fuck....now that I'm writing all this out I'm realizing you're probably going to need a permit. Maybe not for 6 months, but I think that's step 1.