How Can I Use a Non Canon Lens On My Canon T90?

I bought an M42 to FD adapter w/ the idea of using my Helios lens on my Canon T90. After looking at the manual, I am not very clear on how to do the metering. The manual refers to using FL lenses by using the lens in stop down mode and pressing in the stop down switch on the camera. Obviously that wouldn't work w/ the Helios lens. I was hoping to simply set the aperture and let the camera set a shutter speed. Will that work, or am I going to have to manually meter it? I set the camera to AV and set the ISO to agree w/ my handheld meter. When I stop the lens down it agrees, and when I'm in different lighting the shutter speed goes up and down accordingly. So, is that it? Anything else I'm missing?

That should be it
You only need to push the stop down switch to physically close the blades on the FL lenses
It already closes as you turn the aperture ring on the Helios

You shouldn't need to use the external meter in use once you know the shutter speed is reasonably accurate. I use manual lenses on EOS bodies in either AV or M modes, depending on whether I'm using flash or not.

So, yes, that is it.

Thanks I found out that the camera is pretty complicated on this issue! If I press the stop down swithh in, even though it's mechanically not doing anything, it electronically locks the meter setting, which is good. It will still meter up and down just fine like it's supposed to do. If I DON'T press the stop down switch in, then if I accidentally turn the thumb scroll wheel on the top of the camera, which is actually easy to do, then the meter readings go off depending on how far the wheel is turned. It's happy now w/ the stop down switch pushed in, and works in AV mode beautifully. Neat camera.