You will need to create a loop (or find an available one) that only plays a snare on the 4. One measure is enough, but it can be longer...

You then need to put that in the Loops directory
(typically C:\bb\RealTracks\Loops\Percussion Loops)

... and set the parameters within the selection screen when you load the loop.
There is a quick explanation of that on a page on my web site that offers some downloads of claps loops. You might try those out to get a feel for how to do this...

https://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=239513#Post239513