Learn by doing.
A map of clubs and players all around the world.
It is no secret that I am an OGS guy. So an argument can be made that I am not objective, but to my knowledge it is the only server where you do not have to download anything, supports both live and correspondence games and has a great community happy to help beginners with teaching games and reviews if they ask.
While I would suggest to go for some of the traditional servers right away (OGS works in mobile browser), there are some apps that offer quick 9x9 games if you want to practice before committing to an actual server.
A free app with online play, and some puzzles too.
A free app with some lessons, puzzles, and possible online play or against AI.
A relatively strong AI bot, with possible online play.
Have fun playing!