Those transitions should exist inside a folder with the full Transition name. Inside the folder should exist another file with the Transition Name.motr (the file type .motr) plus a large.png and small.png and a Media folder. That is a complete transition "package" for FCPX.
That complete folder needs to be placed in:
your internal hard drive (root drive) / Users / YourUserFolder / Movies / Motion Templates / Transitions
Inside the Transitions folder will be other folders (unless you've never added any other transitions before, or added the supplemental content) -- they are all given "Category" names (e.g.: Stylized). You should either create a New Folder and give it a unique name (Friend's Transitions) or pick one of the existing folders and place the entire Transition folder inside (for each transition you have.)
Back in FCPX, your new transitions should be available in the Effects/Transitions browser under the Category you placed them.
HTH