It looks like you’re referencing an old Nokia Symbian^3 (Anna/Belle) application or system document — possibly a VoIP client or SIP stack settings guide for (EN, full version).
To use SIP on Symbian^3, you must ensure the is installed. Unlike older S60v3 devices, Symbian^3 often required this specific SIS file to "unlock" the Advanced VoIP settings menu.
Select your primary Wi-Fi or 3G data destination. Public User Name: sip:your_username@sip_provider_address Use Compression: No.
(Use the details provided by your VoIP provider)
Under Registrar Server and Proxy Server :
