Hi reck,
To push a barge, first position Atlas as close to the stern of the barge as possible. The bow of the barge has the tall steering cross.
When you click the barge connection button in picture BT1, four connection points on Atlas light up.
When you click one, four points on the barge light up as in picture BT2. Click one to make a connection.
Click the barge connection button again to make another connection.
Regards,
Marty