To do this, visit the Manage Profile page. The link is located in the profile picture dropdown menu. Scroll down to the Introduction Video section and click the Edit button. You will now be able to delete your old link and past the new link here. Do not forget to click Submit - this happens more often than you think! All videos need be approved by the administration so your new video will only be visible once approved.
For information on how to create an amazing introduction video have a look at our article How do I create and add an amazing introduction video to my profile?