When you first sign up for a job seeker profile, you'll be prompted to upload a resume file to help get you started. If you didn't do this, and wish to go back and upload, you can do so with the click of a button.
After logging in, click Profile on the left menu to open your profile page.
In the top right, you'll see a blue button that says "Actions". One of the options under this Actions menu will be "Replace my Profile."
Clicking this will clear your resume of all contents, and let you start from scratch with a resume upload.
Again, keep in mind, this process will erase all resume information you currently have. Be careful!