question about exposure

Hi everyone, I have a question about exposure. I am using a new lens, a canon 40mm on my canon rebel xs. I like using this lens, but I am finding sometimes the pictures come out too overexposed/just a little too bright. For example, I didn't use flash and the drapes were closed, yet some photos I took today were too overexposed. My question is what can I do to help my situation? I realized after the fact that I could've adjusted the ISO, but is there anything else I can try?
thanks.

there are four things you can do to adjust exposure.

Change the Aperture (F stop)
Change the Shutterspeed
Change the ISO
change the exposure compensation

the application of all of these depends on what mode the camera is in. Whilst learning how they relate to each other it can be handy to stick to manual mode, but you will need to adjust them all to achieve correctly exposed photos.

Remember under or over esxposing can also be a creative choice so don't be afraid to pick settings other than what the camera is recommending

Thanks Skyman for the info!!