Sorry, i'm not the one you wanted to answer, but still U_U
First up, even if you know how to draw, digital painting is a totally different thing, so it does not matter THAT much (you can learn proportions etc in a fairly short time)
If you want to start digital painting, the only thing you will need is a graphic tablet, i personnaly recommand Wacom for their low prices (around 70€ / 80$ for a beginner's one) and it comes with a software, wich is really important if you don't want to pay 20$/moth for PhotoShop (maybe you can obtain it by different means hehe)
Dig. painting requires a lot of training, there is really only a small bit of talent. You can find some really good tutorials online (I use tuto.com but i'm french), some are on the official website of PS (i'm not rly sure bout that tho); and a lot of artists make YouTube tutorials. A good way to learn is to copy master's work (like this amazing painting) until you achieve a decent result.
Hope i can help you, and sorry for bad english~