Once you have access to your Kubernetes cluster, you can deploy FTS3 for a given overlay (found in overlays/[dev,prod]) using the Makefile found there with (most simply)
make apply
This will use kustomizations to create or update fts3 and fts3-db namespaces and the resources to run an FTS3 application in those namespaces. FTS3 application containers will run in the fts3 namespace, while the fts3-db namespace is used for a MariaDB Kubernetes operator managed MySQL-compliant database.
This framework uses kustomize to allow modification of YAML templates at deployment time.