Step 1: Install Sideloadly
Step 2: Download the .IPA file
Step 3: Connect your iPhone or iPad to your computer using a Lightning or USB-C cable.
Step 4: Open Sideloadly and select your device from the dropdown menu.
Step 5: Drag and drop the .IPA file of the app you want to install or click "Browse" to select it manually.
Step 6: Enter your Apple ID when prompted, then click "Start" to begin sideloading.
Step 7: Once the process is complete, go to Settings > Privacy & Security > Developer Mode, enable it, and restart your device.
Step 8: Go to Settings > General > VPN & Device Management, tap your Apple ID, and select "Trust." Your app is now ready to use.

Note: For free Apple Developer accounts, you will need to resign the game with Sideloadly every 7 days. You can simply just sideload again with the same Apple ID and Sideloadly will automatically overwrite/refresh the already installed app.