This document describes how to setup a multi tenant app – https://docs.mendix.com/howto/security/set-up-your-first-multi-tenant-app#1-introduction
However it references a Multi Tenancy Administration module which is not compatible with Mendix 8.
How do I configure my app to handle multiple tenants? Have the multi tenancy admin features been bundled in with 8, or is there something missing?
I would first download a Mx7 version of Mendix and start from there. You could export the Multi tenancy module and import that in your Mx8 project. If that does not work you might need to rebuild the concept again in Mx8.