Never knew there were comics. Where would I get them?

I get them at my local comic shop. Dark Horse is the publisher if anda need to order online.

Buffy continued with season 8 in the comics (They are considered canon).
It's currently on season 10 which they berkata would be the last season.
I'd try
www.tfaw.com
or
amazon.com

The sebelumnya poster's suggestion for tfaw.com is a good one. I've bought many comics from there. Another good option is Comixology.com if you'd prefer to buy digital versions rather than paper copies. It's a bit cheaper that way.