Mule consists of a Python API for reading and writing UM files, and a set of utilities which replace some of the standard UM executables such as cumf and pumf. The Mule user guide can be found on the MOSRS webpage (not you will need an account to view): https://code.metoffice.gov.uk/doc/um/index.html
Mule is available on ARCHER for the serial and login nodes. The executables are under $UMDIR/bin/ and the libraries are in $UMDIR/lib/python2.7/.
A one-off setup step is required to add Mule to your Python library path. This can be done one of two ways:
echo $UMDIR/lib/python2.7 > ~/.local/lib/python2.7/site-packages/mule.pth
To use Mule you will need to have Python loaded in your environment
module load anaconda