Any numbers you have already entered will show and you can additional numbers to use by clicking on Add a Caller ID.
Enter the Label and Caller ID and you will get a call to verify that this is a valid number where you can be reached after clicking Add Caller id:
You will then be given a code to enter when you get the call to verify the validity of the number.
You should get an audible confirmation that it has been accepted and you will be able to select your caller id to use when starting a dial session.
** Please be aware that if you are not able to verify your caller id number, that Support can do this for you manually by calling the number and setting it up, however if this is done, you will not be able to use the softphone click to call feature.