The first step is to just play. it might be intimidating at first, but most players and communities are welcoming to new players. It's new players that help shake things up and keep things interesting. And everyone is new at some point. Many people are new multiple times, really, due to taking breaks and similar pauses.

I'd say a good place to start would be to figure out what formats you want to play. Limited is good for beginners as it helps build collections. But it's also one of the most difficult formats to master, as the only way to really get better at it is to play. Watching podcasts like Limited Resources or watching good players stream also helps. But don't be surprised if you don't do good your first time drafting.

Then, there are the constructed formats. Standard is the usual entry place for a lot of players going into competitive scenes. Limited card base and a lower initial cost to entry. Modern has a larger card pool, and a larger price tag to go with it. Then Legacy and Vintage are on top of both of those.

EDH is a super popular casual format. It's a 99 card singleton (meaning you can only have one copy of any card besides basic lands and cards that explicitly state you can have more than one copy) format with a 'commander' that you base the deck around. Check out the Commander decks WotC puts out for a good starting point for it. I'd recommend the 2013 decks due to the fact their tri-color and give you a better starting mana-base.

Once you figure out what format you want to play, just find out when your local game store is going to host that event and go to it. Though if EDH is your game, you can normally go during most Magic nights and see if anyone wants to play between rounds or something. It helps to explain you're new to semi-competitive playing, so people might share some advice. And if you ever have any questions, ask a judge. They're there for rules.