Basic extension installation

I am trying to reverse engineer an installation of a SIP phone on an asterisk server.

I cannot get the extension to be seen by the server.

what is done.

the extension is say 240

the files have been manually created for.
phone240.cfg
.cfg
Dial plan is entered exactly as those of other extensions

the phone is Polycom ip300 . I have useed a telephone that was configured for another extension and working.
I have assigned a manual ip address and also written these into the config file

I have altered only the setings that are specific to the ip address and the extension number in the Browser interface.

but…

I do not see the database ( sip/registry/,ext-num>

the phones mac addresses are used the actual phone setup is that each phone logs on DHCP. At the moment I can’t get the phone to be seen for DHCP. I think that the Database registry is the problem…

any ideas??