Configuring Picasa as my default picture viewer

I am not a geek in terms of computer, but I’m happy to say that I have a newly bought PC. There is Picasa installed on it. I can see the icon from the desktop. So I thought that it can help me edit and organize my photos. But when I attach my digital camera to upload my pictures there is no link to open Picasa. How can I configure my computer and make Picasa as my default picture viewer and default choice when uploading photos? Thank you.
