Hello domsyn,
Fisrt of all, the asterisk side of things for this phone is totally conventional so you can just create an extension in SAIL and choose "General SIP" for your device. Don't bother to fill out the MAC address field but make sure you make a note of the extension number and password which SAIL generates for you.
OK, now for your phone... Log into your phone and go to this window...
http://www.asteriskguru.com/tutorials/thomson_st2030_image272481.jpgUnder
Primary SIP Server, Service Domain, Registrar and Proxy server should all be set to the local address of your Asterisk server. Leave the ports as shown in the screenshot.
Under
User Accounts set the Phone Number and the Authentication ID to the extension number which SAIL allocated to the phone. Set the Password to the value SAIL generated for you. You should be able to set the Phone Name to anything you like but some phones (e.g. Siemens DECT phones) will only work if this value is also set to the extension number.
Log on to the Asterisk console (asterisk -rvvvv) and then apply your changes to the phone and restart it. Watch what happens on the asterisk screen. Your phone should register and come online.
If it doesn't, Asterisk will usually give you some clue as to why not.
Kind Regards
S