OK, your tank typically has 4 inlets/outlets. The big one is the filler usually near the top, a small one is a vent also near the top, then there are 2 small ones of which one goes to your tap and the other is to drain the tank are located near the bottom. They may not be all on the same side like this picture, but it will give you an idea.
layout is similar to some of the bolers, the fill tube is in black and the line to your hand pump on the sink is purple.
This picture shows the where the tank sits under the bench with the blue and white fill on the right and the small plastic tube running under the rear window to the sink.
This picture shows the vent (top) and drain (bottom) on the other end of the tank.
The last picture shows it all from a different view.
Your lines may be positioned a little differently but almost all tanks follow a similar layout. Have a look at where your lines are and try to position the tank to match the lines.