You can't open your doors if you don't know what you're doing. Unless you have blind ambition, the best way to learn the trade is to attend a picture framing training school. There are many around the country. Some last for a week, others for two weeks. This is cheap training, considering the money you will be making once your doors are open.
Schools link is at bottom of page.
If you have the time, an excellent way is to work for a busy shop. Some owners don't like to take on trainees but if you show an honest interest, this is one of the best ways to learn the trade. And you'll have the advantage to see most of the workings of a real picture framing operation. It can be in a corner or a separate room but should be at the location of your actual business. There is paperwork in any business.