Have you got GV working on the phone? If not, reading the manual won't help. Just follow instructions on this site.
https://www.obitalk.com/info/support/ . The basics are the same for all OBi ATAs and IP phones.
And in case it is relevant, the only version of GV that works on the phone is the consumer version. The GSuite version (or whatever it is called) does not.
If you do have basic GV working but want some special feature then you need to specify that.
Please go to the other two copies of your post and use the "Remove" button to delete them.