Click the Wiki link at top for the ctat-mutation documentation.
Easiest to use leveraging Docker or Singularity: https://github.com/NCIP/ctat-mutations/wiki/ctat_mutations_docker_singularity
Otherwise, tTo download the software, click the 'Releases' tab and download the tar.gz.
Note, if you're going to clone the code from github, do it recursively like so:
git clone --recursive https://github.com/NCIP/ctat-mutations.git