If you haven’t played Dungeons and Dragons before, I recommend you read the https://www.dndbeyond.com/sources/dnd/free-rules so you understand how D&D works. There, you can read the basics of how D&D characters are created, the basic rules, etc.
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If you’re new to D&D, start at level 1. With a level 1 character, you can play any Tier 1 game (levels 1 - 4).
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There’s a quick start here: Creating Your First Character, but don’t go there just yet. 😃
Adventurers League (AL) games can be played anywhere that Adventures League rules are followed.
Call your friendly local game stores to find out if they have events or game nights that let you play Adventurers League games.
Be aware that some game stores advertise their games as Adventurers League, but they’re not really AL games. If they’re following “most” of the AL rules, but not all, then we call that “AL-lite” and it’s still not AL-legal.
Big conventions like GenCon, PAX, etc. often have AL games to play.
There are quite a few Discord servers that provide Adventurers League games.
Discord - Group Chat That’s All Fun & Games