As soon as magicJack software window comes up with the message
"Ready to call"
and your phone number (see picture below), you can use your phone or software interface to call to any USA or Canada number
If you are not from USA or Canada and going to use magicJack for international calls, still you can test magicJack by calling to any USA phone number.
Just find on Google the phone you are interesting and make your first call.
If you want to use magicJack for international calls you have to add money to your magicJack account going to the web
and paying by Visa, Master Card, Discover or American Express.
You can dial number using your phone or magicjack application on the screen.