Installing mattermost rancher 1.6

I’m trying to install mattermost on Rancher 1.6 and I was wondering what would be the most practical way of doing this. If I clone into the matterhost github repository for docker I get a directory tree with a docker-composer file and various other directories (app, db, web) which I turn have Dockerfiles and various bash scripts that need to be executed. Within the docker-compose file there the build directives lead to these local directories (build: db; build: context: app and so on and so forth)
So of course I cannot simply upload the docker-composer into Rancher 1.6, because it wouldn’t know where those directories and dockerfiles are.

What would be the standard procedure to do this correctly, if there’s one?
Thanks in advance.