It's not recommended to put toilet paper in a composting toilet because it won't break down as fast in the composting toilet.
But you can put the toilet paper in the composting toilet if you want too and eventually the toilet paper will break down overtime.
All paper including toilet paper will eventually decompose into the soil so you can put the toilet paper into the composting toilet if you want too.
However it's best to leave the toilet paper out of the composting toilet if possible.