This tutorial is for any Lightroom version (Lightroom CC, Lightroom 6 or older, Lightroom Classic) and for presets in xmp and .lrtemplate files.
UNIVERSAL WAY TO INSTALL PRESETS
1. Go to the Develop tab.
2. Right-click on the Presets window and select Import.
3. Choose the preset file and it will be imported.
INSTALL PRESETS IN LIGHTROOM 4, 5, 6, and CLASSIC (Ver 7.2 or older)
The instructions are for Lightroom 4, 5, 6, and Lightroom Classic (CC) earlier than version 7.3 (April 2018) using the .LRTEMPLATE file extension instead of the newer XMP format.
1. Open Lightroom and click on Preferences and go to the Presets tab.
2. Click on the button Show Lightroom Presets Folder.
3. If you're in the Lightroom folder, find and double click the Develop Presets folder.
4. Locate where the downloaded presets (ZIP file) is saved and extract.
5. Copy the presets (from your extracted ZIP) into the Develop Presets folder.
5. Restart Lightroom and you‘re done!
INSTALL PRESETS IN LIGHTROOM CC (MAC or WINDOWS)
These instructions are for Adobe Lightroom 1.3 onwards.
1. Open Lightroom CC and click on the edit icon at the top right. The icon looks like three horizontal bars with circles on them.
2. At the bottom on the screen you will see a Presets button. Click it so the presets panel will be revealed.
3. Click on the icon of three dots at the top. In the drop-down menu select Import Presets.
4. Locate where the downloaded presets ZIP file is saved and select Import.
5. All of the presets will now be listed in the Presets panel.
CAN I USE PRESETS ON MY MOBILE DEVICE?
Yes, you can. If the presets you have include a DNG file, it is compatible with Lightroom app on your mobile device. You can use them on both iOS and Android devices.
However, if you install .lrtemplate file, you must install it in the Lightroom desktop application (not Lightroom Classic) on your computer first. Once they are installed, the presets will automatically sync to your mobile device via the cloud. See also: Step-by-step guide by Adobe.