Step 1
Proceed to Shop.Jeppesen: https://shop.jeppesen.com/shop/. In the upper right-hand corner click the Login/Register button:

Step 2
Enter in login credentials, accept terms & conditions, and then hit LOG IN. You will be redirected back to the homepage. From there, click again on the person icon, then click on Account Details:

Step 3
From Account Details, you can add/update your phone number:

Step 4
Once you click save, the account will be updated.