Download whole project's source code from GitHub and unzip it.
Move the plugin folder (Kdtree
directory) into the "Plugins" directory in
your UE4 project folder.
Generate project files (for example with right mouse click on the *.uproject) for Visual Studio (Windows) or XCode (Mac).
Build the project in Visual Studio.
Launch .uproject file and enable the plugin via Settings > Plugins > Project > Other > kd-tree.