It's super straight forward. You search for "mobius-hotline-server" under Apps, then click on "Get more results from DockerHub", click install.
Then you set up the path mappings yourself under " Add another Path, Port, Variable, Label or Device". According to GitHub, mobius requires "$HLFILES:/usr/local/var/mobius/config"
this means for unraid in the UI ContainerPath would be "/usr/local/var/mobius/config" and HostPath your array path where you want to persist the files. Usually "/mnt/appdata/mobius" or directly on your cache.