You can upgrade you posting any time.
You can upgrade your posting on the confirmation page after you submit your posting.
If you would like to upgrade a posting you have already submitted, go to the the Employers area by clicking the"Employers" tab on any page in the site. Once you are in the Employers area, click on the "My Postings" button in the employer toolbar.
You will need the email address that you used when you created the posting.