Setting up sip account is fairly simple. The sip settings are given on actionvoip page. aw here i post them:
To setup sip on ur phone follow these steps:

1:Get an sip account.
2:under settingg-> voip &im accounts click on new.
3:select type sip.
4:Fill in the settings as given below.
SIP port : 5060
Registrar : sip.actionvoip.com
Proxy server : sip.actionvoip.com
Outbound proxy server : leave empty
Account name : your actionvoip username
Password : your actionvoip password
Display name/number : your actionvoip username or voipnumber
Stunserver (option) : stun.actionvoip.com
5:in advanced sip settings if u click "use for telephone numbers" then option to do an sip call is available directly under individual contacts.
6: keep all the default settings as they are. just change the ones which are empty. click on done.
7: on the desktop click on status bar and set availability to online or busy. only then u can make sip call.

And last but not the least if this helped u click on the thanks button