This article describes how to add a new email address to existing keyring in the Encryption Desktop client.
1) Click on All Keys (see example Administrator keyring).
2) Right-click on Administrator, right-click and choose Key Properties.
3) Click on Add Email Address and enter the New Name and New Email address to add to key.
4) You will be asked for the passphrase of the key. Type the passphrase to unlock the key and commit the change.
5) You should be able to see the new email address added to the existing key in the keyring.