If signing a document is a requirement for your membership, then the membership will be in a processing status until all associated agreements have been signed online; this article explains how to sign those.
From your Home Page, go to the 'Memberships, Licences & Certifications" menu:
If any of your membership has pending requirements, including missing agreement signature, you'll be able to easily identify those thanks to the red tag or one of the 'Action Needed' buttons:
Click on the "Action Needed" button, a popup with the list of agreements missing a signature will display, and you'll be able to click on "complete this agreement" to proceed with the signature steps: