Hi David,
That is just the path that FCPX expects to find Motion templates (default templates that come with FCPX reside elsewhere.)
You can manually create the path by adding the new folders required in the path. So, if in your Movies folder (iTunes/OSX should have created this) there doesn't exist a folder called Motion Templates, then just create it. It is case sensitive and the space is required. Then inside that folder create "Effects" and inside Effects, create a category for your convenience in finding the effect in FCPX, in your case, you could name the folder "Instruction Aids" or something similar -- it is completely up to you! Then, inside that folder, move the entire (Magnifier) Template folder inside and restart FCPX. You should be able to find the effect in the Effects browser Effects > Instructional Aids > Magnifier.
There are 5 possible pathways/folders inside Motion Templates if you want to create them all: Effects, Generators, Titles, Transitions, and Compositions. (This fifth one is for Theme Categories, not something you have to worry about ever, and is used by Motion itself.) The four main folders correspond to types of effects available for FCPX, so it is important to know what type of effect, generator, title, or transition effect is being installed so they can be properly placed to work correctly in FCPX. In other words, "third party" motion templates for FCPX cannot all be placed in the Effects folder. Attention needs to be paid to their "types."
Once Mountain Lion comes out, I'll have to make installers and you won't have the option of naming your own category... 😟