(your model is located on this list, "brscan3") and download the brscan3 and scan-key-tool .deb files. You probably have 32-bit. Then follow the instructions:
Check my posts on this page and a last page regarding scanner installation - if I recall correctly there's a "gotcha" or two. It's not too hard, and if you get stuck don't hesitate to come back here.
You'll be doing all this through the command line. Don't be intimidated, just follow the instructions and make sure not to make a typo (copy and paste the commands to be sure). There are times when you'll have to issue a command as a "superuser" - you'll know if you issue the command and it errors out saying something about permissions. In that case type "sudo" without the quotations ahead of the command. It will ask you your password the first time.
If the instructions say you require packages, probably the easiest way as a new user is to open the Ubuntu Software Center, type the exact package into the search box and install.