Set up help

Could someone please give me a little help? I understand the Asterisk Now software and I understand using an FXO port with an analog adapter going TO my server, but how do I connect my S.I.P. phones to the server? I am looking to have a call-in through a PSTN network, let Astrick software answer, and route to one of three extensions using SIP phones. Thank you.

I’ve not use it, but there is an AsteriskNow Forum that I’d expect would be a better place to ask.