I don't know who the user is who can authorize an enterprise application... can I still do a free trial of OpsCompass.

A user needs to be able to authorize our solution in the environment. However, if you don't know who the user is with this power - you can always sign up for a free account with any of the cloud providers and connect that instance to OpsCompass.

You can sign up for a free cloud account here: 

After you have created your free cloud account you can connect it to OpsCompass.