UNIX

In the directory containing the desired mod files:
    nrnivmodl
    nrngui
Select NEURONMainMenu/Build/singlecompartment.

MSWIN

Launch mknrndll from the icon in the NEURON program group.
Navigate to the directory containing the desired mod files.
Select "Make nrnmech.dll".
Launch nrngui from the icon in the NEURON program group.
Select NEURONMainMenu/File/RecentDir to change the working dir and load nrnmech.dll.
Select NEURONMainMenu/Build/singlecompartment.

single.hoc

load_file("stdgui.hoc")
create soma
access soma
// area 100 um2 means mA/cm2 identical to nA 
{diam=10  L=10/PI}