If youre just beginning, i recommend using paint tool sai. its easy enough to find for free online and a good starting point for digital artists just starting out. Its relatively straightforward, and easy to understand and navigate, Plus theres a ton of tutorials all over the place to help with learning the ropes. For things like layers, it honestly depends on what youre doing, as it varies from piece to piece in digital art.
Some basic sai tutorials:
If you have any more specific questions, i dont mind assisting
im not always on but ill reply as soon as i can, usually.