Hi
the router would need o be reset to factory settings if you have lost your own password to it , they will reset back to admin/password
http://www.cisco.com/c/dam/en/us/td/docs/voice_ip_comm/csbpvga/wrp500/quick-start/wrp500-quick-start.pdf
Page 3
Reset: To restore the router’s factory defaults, press and hold the Reset button for approximately ten seconds.
Phone 2, Phone 1: Use these ports to connect standard analog telephones to the router.
LAN 1, 2, 3, 4: Use these Ethernet ports to connect the router to wired computers and other Ethernet network devices.