Look up how to prepare herbs, from infusions to decoctions, salves to poultices,
Learn the words used to describe herbs and their functions. What is a contraindication? What does a nervine do, an antiseptic, an antispasmotic, a diaphoretic.
Understand that herbalism is NOT like western medicine. We cure by creating balance in the body, not by putting a bandaid on the wound. You need to know how the body works.
Then you need to begin learning about your herbs. Pick a common one first and research it until you're just coming up with repeatitive information. I started out with researching ailments that I or my family had as well as wound care. Herbs that would be useful and utilized.
Once you get an idea of how herbs work and what constituents within them make them work, you'll learn how to recognize those properties in other herbs. For instance, tannins heal burns and stop bleeding. They are normally wherever antioxidants are found, and they are astringents. They are what makes the skin in your mouth feel tight, like when you eat blueberries or drink black tea. Many things contain tannins, some more than others. One day about 7 years ago, I burned myself badly on a light bulb and nothing would relieve the pain. It was mostly 2nd degree and about a 1/8th inch size 3rd degree portion. The 2nd degree was the one hurting (3rd degree doesn't hurt), and the 3rd degree section was too small and minor (white skin) for me to be concerned with. It was late (hence why I was using artificial light to see) and stores weren't open and I was visiting a friend and staying over. Sooo, I grabbed a black tea bag, wet it well, lined it up with the burn and then wrapped my hand in a ripped strip of cotton cloth. 45min later, you couldn't tell I had been burned and neither could I. The 3rd degree section never scarred either.
If I didn't know what tannins do and what has tannins, I would never have thought to use black tea. You won't find that remedy in a book, and the ones online are most likely written by a lady named WhiteRaven or anonymous from Chicago, IL. So learn your constituents and what has them! ;-)