How do you write or transcript music for an Idiophone Instrument?

Hi! So, my last homework of the year is to add an Idiophone instrument to my Orchestra line up and write a song with it.
But, I don't know how to transcript music for it.

The instrument I'm suppoused to use is a Teponaztli, it's like a log drum. It's a pre-hispanic idiophone and I haven't found any score as reference. So... I'm in the dark here, like totally.
I don't know if I should write the part for it as a Percussion or use notes like a Piano. Grand staff I mean.

Anyway, I hope you guys can help me out with this one. Thanks everybody for your support! (: