Here are some pictures supplied by Camnbron of his 4 foot tank when he had just finished constructing it. This is an excellent pictorial example of how to correctly set up a 4 foot tank.
The tank
The sump in the cabinet underneath. Note the return pump, and the skimmer. There is also room for more equipment in the future
The overflow in the corner of the tank, which allows water to flow down to the sump
More pictures of the overflow. The white pipe is called a Durso Pipe. It is designed to allow water to flow from the overflow to the sump, without any gurgling noise, or at least a minimum of noise. There are other outlet pipe systems also, the Durso is one of the most popular.