To send domains using the UD app, you must:
1. Head to the home page of the app, and press on send,
2. Enter/Paste in the recipient address,
3. Once you tap on the address you are sending to, navigate to the domains tab, and select the domain you wish to send, then click continue,
4. Verify that you are transferring the domain to an address and that it is not an exchange address, then hit confirm.
5. The transfer will initiate and you can track the progress by locating the domain under the domains tab in the home screen.
The video below shows an example of this process: