You need to turn on developer access on your phone. This may differ between phones and devices, here is how I did it on my phone.

Go to Settings, and scroll down to click on "System".

Scroll down to "About Phone" and click on this.

Scroll down to "Build number" and click this 7 times. You should see it starts to tell you "you're about to become a developer". Once you've clicked 7 times, Developer Options should appear in your System settings.

Next, you need to locate and turn on USB Debugging, in your newly enabled Developer options. Scroll down until you find it, and turn it on.

To install the new apps you are going to be creating, you need to find and turn on "allow unknown apps". Again, the location of this may vary from device to device, but here is where it is on my phone.

Go to Apps and Notifications

Go to Advanced

Go to Special app access

Go to Install unknown apps

I've chosen to go to Files, as I am intending to install my app by direct file transfer. You might want to enable Chrome if you're intending to download it, or Gmail, if you are going to email it to yourself.

Your final step is to connect your device to your Mac, using a USB lead. The first time you do this, you should see a dialog asking if you trust this computer. Confirm, and you are all set to start installing LCFM Native apps on your device.

You may also have a tick box on the allow screen, to Always Allow. Check this to ensure you can install apps on your device more than once.