Make a service file for it! You can use an existing one as a model. Or follow
this guide. Also, from what I can remember, all the systemd ancillary file types are very well documented in the man pages. They are based on an old Windows config format whose name I forget.
One of the driving forces towards widespread acceptance of systemd was that configuration using these files was considered easier than writing init scripts for starting and stopping services. I've come to think that this isn't worth the extra complication in the internals of your system, but I can see the point of the argument.