Only user with Administrative role of the domains can assign. Here are the steps:

1. Login to SELFCARE.
2. Go to Domains. Select Transfer Between Accounts.
3. Select domains from the list. You may select up to 10 domains.
4. Click Continue.
5. Enter the name and email address for the new contact.
6. Review and tick the acknowledgement. Click Send Transfer Request.

The user from the other account need to accept within 3 days.