How to link ports

I have two extreme switch devices which are connected on a port, but there is no link between two ports in the webinterface.

How can I (manually) link these two ports?

This is a cisco switch where it does work:

This is the Extreme switch where it does not work:

Links are discovered by XDP(CDP/LLDP/FDP). Enable it on your extreme switches

There is no way I can do this manually?

No you need to enable that on your devices also check out for discovery.