Install the Demo app and use a non SRV connection string. Make sure your MongoDB cluster either is open to all IPs(0.0.0.0) or you whitelist the client IP.
Use the CRUD actions from the extension "MongoDB Extended Services" to do the operations on MongoDB.

Where ever there is a Sort input use the values like "{_id: 1}"

If you do not have any filters or projection, instead of leaving the input fields as blank pass "{}"
For, DocumentFindByIds use comma separated Mongo object Ids : e232234fsd32323442w, 789ds131321asdasd
For "AggregateGroup" action use values like this for the GroupJSON parameter:-