Change the "end bar" number by however many you plan to add.

Go to the spot you want the extra bar(s). Put your cursor on the first bar AFTER the silence or bars you want to enter. Select everything from there to the end. Cut it, move the cursor where you want to start again, and paste. A more advanced method is to select, hold the ctl key down, and slide it to the new location, in your case a full bar or 2.