How can I create multi-app container?

I have installed Docker on my Synology NAS so that I may install and experiment with elastic enterprise search.
Docker was installed via the Synology Package Centre, and I’ve also installed docker-compose and Portainer - thanks to guidance from https://www.youtube.com/c/WunderTechTutorials.
I was able to install enterprise search using portainer (see below)

, but it would only run for a few seconds.
I guess that this is because it requires Elasticsearch.
But, how do I install 'em both in the same container?
There are a few, sample, multi-app docker-compose.yml files on elastic.co, but I couldn’t get any of them to work, and I was so happy when I found Portainer, and a comparitively simple container creation process.
I couldn’t find any techniques for creating multi-app containers using Portainer.
Any suggestions, please.