How do i create a multiclass character in the menzobarrenzan character creation screen?Im trying to make a fighter/cleric elf and a mage/thief human.the menzobarrenzan creation is not forgiving at all hahahah.

any help would be appreciated folks and thanks ;)

The DnD rules are old in this game, so certain things are not allowed.
You can't multiclass humans in the Ravenloft games (I think a bunch of old DnD 2E DOS games don't allow this) and fighter/cleric elves aren't allowed either.
You can make a fighter/mage elf, or a fighter/cleric half-elf. I'm afraid you'll have to experiment.

Multiclassing did not exist for humans in AD&D 2nd Edition. When you create an elven fighter, you can add mage or thief classes. If you want a fighter/cleric, I would suggest a dwarf. A dwarven fighter/cleric and an elven fighter/mage is the best party for the ravenloft games anyway.