[SS Tim]

Its easy enough. First thing I recommend is everyone have a set of factory manuals. There are online copies you can download that are workable interim (see my signature).
Since you didn't give much information are we to correctly assume you are asking about the factory NL2 left side tank and it is listed on your SPID?

If it was added or a dealer installed there may be differences.

In operation it (NL2) is a manualy selected tank via a floor mounted valve and lever handel. It also has a fuel gauge selector switch on the far left dash, left of the cluster. This only switches the gauge not the fuel.

Most of the information you would like to see is in the "assembly manual". This is more or less a collection of assembly oppperations concentrating on options installation. There is a lot of good information but its not paginated nor indexed. There is an index here on the board assembled by members but I haven't used it.

Here are a few pictures to get you started.
The fuel lines snake back and forth under the cab from the hardline to the tank and the selector. Don't have a diagram on hand at the moment, sorry.