Adding Percussion to this Score

Hi .. I'm struggling to work out how to add a Susp Cym Crash to this score (and into the Sd part specifically) at letters D/G and Bar 83?

My friend is a Brass band Arranger and sent the file over as an XML file (if that makes a difference?)

Musescore doesn't seem to let me add an extra Percussion track either? Hmmm?

I downloaded the General Percussion Midi info list (attached) from Musescore and it looks like '49 C#2' is a Crash Cym...but it's playing back as a Snare click or something other than a Crash Cym?

Also the 'Edit Drumset' drop down box seems to be empty of Instrument names? (Musescore Perc) (Attached)
Do I need to 'load something and save? or why is that Perc list blank?

I've attached the Musescore Score ........Bom Bom ANDY FOR PERC EDITING A.mscz

Totally scratching my head on this one!

Thanks in advance for any advice!

Dave