Cisco SPA 303 3-Line IP Phone

Does anyone know how to add a second line to the Cisco SPA 303 3-Line IP Phone supplied by Ooma?
I cant noodle out the Cisco documentation supplied with the phone, and the chat support says the Ooma sales description means you can put three calls on hold, not add two more extensions to the phone.

REF the Sales Description:
“Cisco SPA 303
3-Line IP Phone
Cisco’s Small Business SPA 303 IP Phone features exceptional voice clarity and enhanced speaker quality. It has a 2-port Fast Ethernet switch, a monochrome LCD display, 3 line keys, 4 soft keys, and a 2.5 mm jack connector for optional headset. It supports up to 6 simultaneous calls.”

Thanks

Oops I fat fingered this into the rong subject, should be in other support…