If you don't remember your password, click the link below and look under Troubleshooting, # 2.  If you don't think you ever set up your voicemail, then look under Using Voice Mail, # 1 and if that doesn't work, contact Customer Service (dial *611 from a cell phone or (800) 922-0204) to get it set up.

Voice Mail FAQs | Verizon Wireless