Sign your full name.
Sign "B.Sc." or "B.S." at the end of your name, after a comma. Both designations are used and both are correct.
Include the title of your degree if you wish. If you are writing a scholarly paper that will be published, you might want to include the type of B.S. degree you have, especially if it is directly relevant to the topic you are writing about. This will verify your expertise in the subject. For example, if you are publishing a paper relevant to the field of criminal justice, you may wish to sign your name with a "B.S., Criminal Justice" at the end.