Along the very top of the page is a Ad, under the add are the following options
Chat-Search-members-calender-user cp-donate-raffles
Click on User CP
when the page loads there is another row of buttons
My vB home, Manage Files, Edit Profiles, Edit Options
select the Edit Options
When the page loads scroll to the very bottom where it says Avater on the left side.
Select change Avatar
When that page loads at the very bottom is a text box to place in the hyperlink to your new sig file. It has to be 100x100 in size etc.