Use 2^nd Device as Remote

On your mobile device select "Remote" after launching the app. The remote should then connect automatically to your PC / Mac.
If it does not the reaseon for not finding the other device can be the strict firewall rules on your PC/Mac preventing connections. On windows you have to allow all connections for the app in both (incomming/outgoing) directions.
Macs might ask you for permission - you have to allow this!
If still not connecting, you can try the “reverse” mode in the settings on both mobile and pc. This will set the remote in "listening" mode waiting for the PC/Mac to connect.

If still not working:
Make sure both devices are on the same wi-fi. If pc is connected by cable make sure, the ip range is the same.
Example: mobile on 192.168.1.123, pc on 192.168.1.124
The numbers to match in this case are 192.168.1.* - could be different in your network - but first 3 numbers must match.

... still not working:

If the remote cannot find the other device go to the settings > network in the main app (not remote). Then tap "reverse mode". On most devices this brings up a system warning "allow app to access local network" or similar. Accept this.
Then turn off "reverse mode". Now the remote should be able to find the main app.
If not you can also try the same on the remote app or even keep "reverse mode" on both devices. In this case the main app will try to find the remote.

In some cases the scanning process gets stuck - that means the app is not reacting. Usually after one ore some minutes it works again. The reason is the network layer not being able to scan the network or being "trapped" by a non responding device on the subnet it wants to scan.
In this case it might be better to enter the IP adress of the "other" device manually.

There is no limit for remotes to connect to a single PC/Mac. So you could use more than one remote. But this only works in the "non-reverse" mode!