To connect your datastore to your Proxmox Virtual Environment (PVE) Server, you can simply add it as a new storage.

For that, login into your PVE Server and on the cluster-level, navigate to storage and click on "Proxmox Backup Server" in the "Add" dropdown:

You can copy over the information that are provided in the "Connect" Modal on the Datastore-page:

After that, navigate to a VM and create a new backup, select the correct storage and create it. You can of course also create a normal backup job, it's a datastore after all!