Tested with version 1.0.1.
Select menu: Go->Preferences.
NAT traversal options should be enabled if you are behind the NAT.
Firewall external IP should be specified.
Identity. Your sip address. Use your Account Id here.
Save your preferences.
Now you can dial regular phone numbers.
E.g. for dialing USA number +18001002000 at main panel of the phone in "sip
address" area you should enter the phone like:
Proxy to use: None.
On first call attempt you'll get "Authentication request" dialog.
Authentication required for realm "usgw.ast.diamondcard.us"
Username: enter your Account Id here.
Password: enter your PIN code here.
After that linphone will memorize you authentication data and wont prompt
you on each call.