To connect from another PC running Windows 10, head to Settings > Display on that PC and select “Connect to a wireless display”. This setting should be in the same place on a phone running Windows 10 Mobile.
The PC running the Connect app should appear in the list. Click or tap it to connect.
After it connects, you’ll see a few more settings. Enable “Allow input from a keyboard or mouse connected to this display” and the PC functioning as the receiver will be able to interact with the PC through the Connect app.
To change the project mode, select “Change projection mode”. By default, it functions in “duplicate” mode and duplicates the contents of your screen. You can instead choose to extend the screen and treat the remote display as a second monitor, or only use the second screen.
Whichever option you choose, you can enable full-screen mode by clicking the “full screen” button on the window title bar.