My question is simple. I recently discovered that chess.com hosts a computer chess championship, and that got me really interested in chess programming. I know its a very difficult field, but let's suppose I do create a chess engine someday. How could I enter it into a tournament? Is there a ranking system for "chess computers"? Are there lower level tournaments which I have to win to be able to participate in a bigger tournament like CCC on chess.com? I tried running a quick google search but found nothing. I tried searching for the big "Participate" button on the computer chess championship section of chess.com, but I couldn't find one.
You will need to create a chess engine, and then announce it out on talkchess. There will be independent testers who will run your engine in their own tournaments. You will see your engine appear in various computer rating lists.
If your engine is open source, there will be engine programmers checking if your code is a modified Stockfish. If YES, you won't go anywhere but very low ranked computer tournaments. If closed source and you have a very strong engine, the community will compare your engine with Stockfish.
TCEC won't enter you unless they are sure your code is "original" - not a copy-and-paste from Stockfish. You need to demonstrate not just that you have an engine but your works are original. Your engine will also need to play strong chess (at least GM level).
Once your engine has been "accepted" by the community, you don't need to do anything because TCEC will most likely contact you and enter your engine. They will work out how to find you.
If you just want too see how your engine fares against players, easiest to implement are probably Lichess bots. They however cannot participate in Lichess tournaments, nor enter its leaderboard. Thibault wrote some advice for implementators here.