If you want to try playing with random assholes on the internet, go to roll20 or some other site. Alternatively, go to /tg/, you can find a game there, either in one of the dedicated threads for one of the DnD systems or in a gamefinder thread.
If you want to play with real people, step one is to attempt to make friends.
Step two is hope they also want to play. If not, return to step one and acquire more friends.
Step three is fucking play.