An official WireGuard client for Android is available in the Play Store

Once installed, open the app and you will see the following screen

Press the + button and select Scan from QR code and then scan the QR code image on the IPFire WireGuard WUI page

Enter a name for the Tunnel as shown above and press the Create Tunnel button.

The WireGuard app screen will then look like

Select a profile and click on the name and a screen showing the contents will be provided.

Go back to the previous app screen and press the button the right hand side and it will switch on and the colour will change to blue when the WireGuard tunnel is active.