Go to the "Profile management" section in your Personal Account area (hover over your name in the upper right corner).

In the "Personal details" section select "Verify email" / "Verify phone number" or click "Edit".

Follow the instructions shown on the screen.

Go to the "More" section.

Click on your name at the top of the page.
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Go to the "Personal details" menu.

Click on your phone number or email.

Follow the instructions shown on the screen.