The installation method for MOPs is much simpler now than when we first launched. You have two options for installation, depending on what Houdini version you're running and your own personal preferences. If you're running Houdini 17.5 or later, it's recommended that you use the "package" installation method.
The full MOPs installation instructions are available on the MOPs Wiki: https://github.com/toadstorm/MOPS/wiki