Typically, your carrier’s voicemail system guides you through the process of listening to and managing your voicemail. The first time you call your voicemail, it also guides you through the process of recording greetings, setting a password, etc.
Tap the Home Button > the Phone icon > Dial tab.
Tap the Voicemail button (on the dialpad) to dial your voice mailbox.
Follow the setup tutorial.
Enter a password.
Record a voice signature and greetings for your voice mailbox.