There are a few routes to take. If you want to make money sooner, find a salon that offers education. A lot of the chain salons will offer training prior to taking clients. You can also ask cosmetology schools in your area if they offer refresher courses. Typically this is a "self study" program that allows you to practice with the aid of educators nearby. There is typically a cost associated with a refresher course.
Doing hair is very similar to riding a bike. You mostly will just need to start and it will all fall into place. Good luck!