The easiest thing to do is create a batch file (.bat) with the commands to run it.
But, basically, it's the following syntax :
eduke32 /x<Path to Mod>\<Con File> /g<Path to Mod>\<Group File>
Where <Path to Mod> is whatever subDIR you put the levels in. I suggest putting a Levels DIR in the main Duke3D DIR so you can keep things clean. IE - Duke3d\Levels\
No space between the x in the /x and the <Path to Mod>. Same thing with g and /g.
eduke32 /xmetropolitan.con /gmetropolitan.grp
eduke32 /xaddons\nwinter.con /gaddons\nwinter.grp
Post edited June 23, 2013 by Firebrand9