You can store and recall sip address using the address book (in the connection menu). A sip address is in the form: sip:user@domain_name. You can also add a display name, that is used only for your information. To recall a sip address, select it in the address list, and click on the "select" button. Then you will see the address you have selected in the main window. Just press the call button to call the person.