If you have a User Login for SEED applications (SeedViewer, RAST, MetaRAST and others), you can easily log in using the Login Box present on the right side of the menu page on every page (unless you are already logged in).
Enter your login in the first textbox, and your password in the second, then press return.
After logging in, the Login Box will be replaced by your first and last name, together with the small items displayed below. The little door icon lets you log out. The other icon leads to your User Management Page.