Yes, you can do it.
However, the big thing that would decide how to do it is what you will see when you take off the side panel of your computer. What type of cable, is there a spare connection on the current one, is it IDE or ESATA, do you have room, etc.
The process is really simple, but if you haven't done it before then things might look a bit confusing.
My suggestion would be to go to youtube.com and do a search on adding a second hard drive. Then you can watch and see others explain how it is done and it will help you get the idea.