options:
1. build to 10x their power, then declare independence
2. ask them nicely to release you
3. remain enslaved, it`s no big deal, maybe they`ll supply you some ships in return
Considering you just started today, option 1 is probably out of the question for now unless they come lower than where they are now. Getting enslaved doesnt mean you are bad at the game, it`s just a part of the game.