Make sure the folder containing your .xmp presets is saved in a location where you can easily find it.
I suggest unzipping it and saving it on your Desktop.
You will want to copy this folder so that you can paste it into the settings folder later. Read the step by step directions below to walk through the process.
1. Open Lightroom Classic. In the upper left hand corner, click on Lightroom and then click on Preferences.
2. A new screen will pop up. Look for the Presets tab.
3. Click on the white box (towards the middle of the screen) titled Show Lightroom Develop Presets.
4. Locate the Settings folder and double click to open it. Paste the entire unzipped folder containing your .xmp files (the one you unzipped and copied earlier) into this folder.
5. That’s it! So easy and fun. If the presets do not show up automatically, go ahead and close Lightroom. Once you re-start it, the presets will appear.