Depending on the buyer's preferences, you may need to transfer the domain to another registrar or simply move the domain to another Dynadot account.
If you are moving the domain to another Dynadot account, you should first ask the buyer to create a free Dynadot account if they do not already have one. The account creation page can be found at this URL:
Create an Account http://www.dynadot.com/create_account.html
Once the buyer has created their own Dynadot account, you can move/push the domain into their account by following these steps:
1) Log into your Dynadot account. 2) Click on the "Domains" link in the main menu at the top of the page. 3) On the "Manage Domain Names" page, choose the domain(s) you wish to push by click the check boxes and press the "Change Account" button. 4) In the "Domain Change Account (push)" enter in the recipient's username and email address in the text boxes. Click the "Change Account" button to initiate the move.
An email will be sent to the recipient of the domains asking them to confirm the move.
The buyer may initiate a "Change Domain Ownership" order themselves by filling out the form here: