When using an adapted manual-focus lens on a Canon dSLR, you have to use either the M or Av mode on the camera. No other modes work properly, because the camera cannot tell the lens to change the aperture setting. Aperture must be adjusted via the lens's aperture ring, and ISO is adjusted on the camera body, as you normally would.
In M mode, the exposure compensation scale at the bottom of the viewfinder now acts as your light meter. The 'needle' does not automatically get set to "0" as it would in Av/Tv/P/Auto. You have to put the needle there manually using the aperture ring on the lens, or adjusting your iso and shutter speed on the camera body. "0" may not be 100% correct, but it's where your camera would have put the exposure in one of the automatic modes, and should usually be in the ballpark.
You also have to focus using the focus ring on the lens, and it may be difficult to judge accurate focus once the lens stops down, because in order to get accurate metering, the camera should be stopping down the lens to measure the amount of light coming in. You may want to set the lens to wide open and focus before you adjust the exposure settings. And if your adapter was chipped for AF confirmation you can also use the green dot lighting up to judge focus lock, but I found it variable on accuracy.
But chips vary. I had one once that reported EXIF and AF confirmation, but it screwed up the metering in the camera by faking that I had a lens that would be wide open for metering and stopped down for the actual exposure, and whatever I had set on the lens had to be compensated for on the meter (i.e., if I shot with an f/2.8 lens, and I wanted to stop it down to f/8 for shot, and I'd set f/8 on the lens, I had to make sure the meter showed me I was -3EV). I've had others (that reported EXIF (including the aperture setting used) and AF confirm or just AF confirm) that worked just fine with stop-down metering. So, metering is another variable to consider.
My recommendation, if all this is too confusing, is to start by shooting in M mode with an EF-S lens, so you get conversant with how it's all supposed to work and what the individual settings do to an image and to exposure. (Bryan Peterson's Understanding Exposure is also a good reference for this). And once that's all sussed out, try again with the adapted lens.
This is also why I tend to recommend getting native-mount autofocusing lenses. After adding in adapter cost and PITAness, going with a manual adapted lens is really only for the super-stubborn, collectors, and video folks. :)
See also: Can I use lens brand X on interchangeable lens camera brand Y?
