It is pretty straight forward, you position your cursor on a row in the band activity window, you should select the row that has the call sign in it that you wish to make contact with. Once you double clicked on a row, and your cycle comes up (15 seconds increments, WSJT will start sending, the Enable Tx button will become red and you should see a red highlighted bar in the left hand and in the right hand window. After that, will have to wait for the other station to respond to your call.