If you want to add new identity for the application (if you want another user to access the application), you first have to select your own identity and enter the correct password. After that, you can press the button to create a new identity. Remember, that not all of identities can add new identities (you choose this right during creation of the new identity). If the button for adding new identities is disabled, you cannot create new identities.
Suppose you entered the correct password and pressed the button to create a new identity. A dialog for information about the new identity will open. Now, you have to enter the name of the new identity and it's password (twice to verify the password). Moreover, you can choose whether the new identity can add another identities (see above).
Both name and password can have only 14 characters.
It might be possible to have more identities with the same name, but we strongly do not recommend that.