After you have registered your SIP phone, making calls is basically no different then when you make a call on your mobile of cellular phone.

In the USA, you would dial standard 7* or 10* digit number and then press the required button on your SIP phone. This button could be different depending on your phone. Some say Enter, Call, ,Talk or Dial. In some cases, your SIP phone can be programmed to dial automatically when the 10th digit is received.

For international, if you have that service activated you would dial 011 + Country Code + number and push the button.