Formal:
* J'ai terminé. (pronounced "zhay ter-mee-nay") - This is the most literal and formal translation of "I am done."
* J'en ai fini. (pronounced "zhon eh fee-nee") - This means "I have finished" and is also quite formal.
Informal:
* C'est fini. (pronounced "say fee-nee") - This means "It's finished" and is more informal.
* J'ai fini. (pronounced "zhay fee-nee") - This is a more casual way of saying "I have finished."
* J'ai terminé avec ça. (pronounced "zhay ter-mee-nay ah-vek sa") - This means "I'm done with that."
The best way to say "I am done" in French depends on the specific situation and the level of formality you want to convey.