To add a contact on a Grandstream GRP2612 phone, you can follow these steps:

1. Press the "Menu" button on your phone.
2. Use the arrow keys to navigate to the "Directory" option and press "Select".
3. Choose "Add Contact" and press "Select" again.
4. Enter the name and phone number of the contact using the keypad on your phone.
5. Press "Save" to save the contact.

You should now be able to find the contact in your phone's directory and call them directly by selecting their name from the list.