1. First, make sure you have Simbody installed and functioning on 
your machine *before* installing Molmodel. Go to 
https://simtk.org/home/simbody.
2. Optionally, install OpenMM if you want to use a GPU-
accelerated force field. Go to https://simtk.org/home/openmm.

THEN:
1. Choose the release version you want (e.g. Molmodel 2.2).
2. Decide whether you want a precompiled binary (recommended) 
or the source distribution. Then follow either 3 or 4:

3. Precompiled binary: 
   - Pick the platform you are running on: Linux, Mac, or 
     Windows.
   - From that platform's set of zip files, pick the one
     that exactly matches the binary release of Simbody you
     used.
   - Download and unzip. You can put it anywhere and then 
     move the whole directory structure later. 
   - Look in the "doc" directory for the Molmodel User's Guide
     and read the installation instructions. The User's Guide 
     is also available in the Documentation section of the 
     downloads page.

NOTE: you should install Molmodel in the same directory that you 
used for Simbody. Just copy the Molmodel files into the 
installation directory -- the names do not conflict.

4. Source:
   - Be sure Simbody is already installed (typically you should
     build Simbody from source if you're going to build
     Molmodel from source).
   - Download and unzip the Molmodel source distribution.
   - Look in *Simbody's* Documents directory for 
     the How to Build Simbody from Source document for 
     your platform -- Molmodel works the same way and doesn't
     have separate instructions except in very abbreviated 
     form in the Molmodel User's Guide.
   - Read and follow the build instructions. Be sure to set 
     the installation directory to the same place you used for
     Simbody.