Assuming you are using new Lightroom versions (7.3 or later versions). They introduced a significant change in the way Lightroom works with presets.
Previously the Lightroom presets extension was .lrtemplate which is now changed to .xmp. Good news is, if you have older (.lrtemplate) presets and if you are updated to the new Lightroom versions, all presets will be converted to .xmp automatically.
The Quickest Way To Install Lightroom Presets
- After downloading the presets unzip it if they came to you in a zipped format.
- Make sure you have .xmp files ready
- Open Lightroom and click on Develop module
- Click + on your Presets tab and click on "Import Presets"
- Select the Presets (.xmp files) and click on import.