olympus om2 and speedlite

hi, has anyone used the canon 320ex speedlite with the olympus om2?

i am able to connect the speedlite and a flash goes off when i have the camera on auto and press the shutter. however, i am unsure if the exposure is correct, i have no idea.

the manual for the om2 says a red light in the viewfinder will appear when the exposure is correct, but i don’t see that even though my batteries are fine.

i have no idea how to gauge exposure with this. sorry i am also new to using flash and i haven’t done it with film photography before. if anyone has any advice that would be extemely helpful, thanks!!!