This is really simple. If you're just starting out, its just about having fun while playing tennis. Don't be too caught up about technique if it kills your fun. However, if you're serious from the get go, then you should come up with a plan.
Without a doubt , the best way to get started is to get a tennis coach. Otherwise, playing without a coach is easy, just get onto YouTube where there are many videos on how to get started playing tennis be it a forehand, backhand, serve or volley. Self-learning can be tricky as you don't have an eye to watch out for your mistakes and might end up with injury while playing with the wrong technique.
If you are intending to pick tennis as a skill then you might want to give yourself about 3 months as an estimate to learn the sport. However, to be relatively good at it , it depends on individual as everyone is different. Therefore, you can certainly go through all the techniques required within the few months to grasp the game but being good at each stroke of the game is subjective.
The most important thing about playing for beginners is to have fun. Get a friend or a group of friends to the tennis court with tennis balls. There is a range of colored balls with difference bounce for learning. Pick one that might be suitable for your group's level or yourself to rally.