How do i stream with my MBP turned off?

Hey

Is it possible to stream my music from my time capsule with my MBP turned off?

If so how?

Not possible today with the current AppleTV OS.
The only way to maybe make this work is to jailbreak your AppleTV and install AFP or SMB support then mount the time capsule via AFP/SMB

ATV flash is installed and the time capsule is mounted, am i missing something?

some kind off setting maybe?

Nope.. you need to sync rather than stream. This is what I do with my music on the aTV

Streaming requires a copy of iTunes to be running on the machine that the apple tv has linked to as an iTunes library.

The time capsule is an embedded device - it just provides storage