Add Objects to tree

We have eDir 8.8 on a few servers, and I am still a rookie.

I am wondering, how I can add Windows Workstations or Linux Servers to the tree.

For example, I have a Linux (OpenSuse) VPN-Server and Windows Laptops. I would like to use the PKI of the eDir. But I can assign certificates only to objects in the tree. So how would I add such servers (without making them full eDir servers that hold a replica) and Laptops to the tree?

Thanks.

Michael