Plugins have to be placed in precise locations in order to be "seen" by FCP X.
Please post a screenshot from the Finder, in Column View (command-3) showing all the way from your Movies folder to the actual plugins.
The general structure for effects (and similarly for other plugins) is
/Users/(yourname)/Movies/Motion Templates/Effects/(Category)/(Plugin-folder)
where:
(yourname) is your username - in other words, the aforementioned Movies folder is the that already exists inside your home folder
The "Motion Templates" and "Effects" folders must be named exactly, and furthermore, they need to be "localized".
Select each of these folders in the Finder, press Command-I and make sure to add an extension ".localized" if it is not there already.
Name the (Category) folder in any way that makes sense to you. This is the name under which those plugins will be grouped in the FCP effects browser.
Put the whole folder containg the plugin inside the (Category) folder.
Do NOT "localize" either the (Category) folders or the actual plugin folders.