To find the link to the partner accounts, you must be signed in to FamilySearch.org with an LDS Account (i.e. be a member of The Church of Jesus Christ of Latter-day Saints). When you click on the Get Help link, you will see a drop down menu like the following. You click on the Help Center link.
The Help Center page looks like this:
The arrow is pointing to the Partners Link. This is a screenshot of the Partners Link:
Here is the page for MyHeritage.com:
Here is the page for findmypast.com:
Each of the pages has extensive help documents and flyers to give information about the process of obtaining free access to the individual programs.