Go to vMPF. On the top menu you’ll see “Home”, “Assignments”, “Miscellaneous” etc. Underneath Assignments, you’ll see “Projected Assignments”. On that page, print out the page to a PDF, and based on your local requirement put digital signatures on the areas at the bottom of the page. Fill out that form and then submit it to your MPF.

https://www.reddit.com/r/AirForce/comments/1alsgxi/pdd_change/