How are the beats represented in GarageBand?
Is it just because you can see the waveform?
If you need to, you can Detach Audio and do this simple visualization in FCPX as well. Enlarge the audio clips usig the Clip Appearance window bottom-right.
If I was serious about doing this, or the waveform didn't make the beats obvious, I'd load the song audio into LogicProX (maybe GarageBand) and find a way to create a new audio track with just the beats in it.
So, you could record your own track alongside the real song with just you hitting a drum sound in GarageBand. Then load that audio into FCPX and the waveform should have very obvious visual indication of those hits (because it's the only thing in that audio track)
There are ways to make that more precise - but then we're moving into the area of music production.
… since I am not very musically inclined…
Do you like to dance? … ok, alone, when nobody's watching ?
Editing 'stubborn' to a technical beat creates some boring output; what I like to do is:
select the music-clip in your project
hit 'play' and put your finger on the key M
…now start to dance to the music
(tap the m-key whenever it fits)
What I like to express is:
music has drama, accents, pauses, highlights, … and beats.
When I tap to music, I get a much much better 'beat' for editing than by measuring 116beats-per-minute into my video.... watch how pros edit to the music - mostly NOT on the beat, but before or after or 'around'.
… just as a suggestion …