For example, to see your currently loaded modules, type module list. To load the gaussian package, type module load gaussian. All packages will have a default version that gets loaded if you don't specify the version - if you want a specific version, specify it when you load it, e.g. module load mrbayes/pgi-mpi-3.1.1.

You can also write your own modulefiles in ~/privatemodules, then load those. There is an example module file documented on privatemodule. Also, if you have an environment you want at boot, you can create ~/privatemodules/default (which should be a list of module commands like the following:

module load radmind
module unload openmpi/1.0.2-pgi
module unload pgi/6.1
module load nag
module load mpich/1.2.7-nag

Here are some Module subcommands that might be helpful (ie. module help):

help:

Print the usage of each sub-command.

load modulefile:

Load modulefile into the shell environment.

list:

List loaded modules.

avail:

List all available modulefiles in the current MODULEPATH.

show modulefile:

Display exactly what modulefile sets and other information

whatis modulefile:

Display the modulefile information set up by the module-whatis commands inside the specified modulefiles.

apropos string:

Seeks thru the whatis informations of all modulefiles for the specified string.

You can get more information and options by typing man module.