I have a song in 4/4.  I would like to add in the last quarter of a bar 3 snare hits (an audio file of the snare) as triplets (meaning 3 snare hits equally spaced in the last quarter of a bar).  How can I achieve this - do I need to change the time signature at this point for this track, or adjust the quantise setting or snap setting, or something else?  I'm thinking it should be possible to drag the snare hits and they snap into place ...?

ULTRABRA
I have a song in 4/4.  I would like to add in the last quarter of a bar 3 snare hits (an audio file of the snare) as triplets (meaning 3 snare hits equally spaced in the last quarter of a bar).  How can I achieve this - do I need to change the time signature at this point for this track, or adjust the quantise setting or snap setting, or something else?  I'm thinking it should be possible to drag the snare hits and they snap into place ...?

 
Change the snap setting to 8th triplets while you are working on this phrase.  Change it back when you are finished.

Yep, Snap is key here.
 
You can also change the grid resolution to triplets so that when you add your 3 notes, you can SEE they line up properly