The following should be the current direct link if you are logged-in to the website (if you are not, it should prompt you to log-in and then take you directly to the page):
Request Past Flight Points
Here's the text of the page too:
"You can request past flight points for travel completed within the past 12 months.
Only flights taken over 48 hours ago will be reviewed for past flight points.
Name and date of birth associated with the passenger's reservation must match the name and date of birth in the Member's Rapid Reward account.
Travel on Rapid Rewards Awards, Companion Passes, non-revenue (free) tickets, or charter flights are ineligible for points.
Past points request for our Partners must be submitted directly to the Partner.
For more information on receiving past Partner Points, see our FAQ