Toilet water leaking

[yipykyah]

I have a Forest River MacII pop-up with a Thetford cassette toilet. Apparently, during the winter the water container for the toilet wasn't completely drained and suffered freezing damage. When I add water to the toilet, it leaks out on the floorboard.

Does anybody know what I have to remove to get the the inner plumbing of the toilet water reservoir?

ETA: It is a C-400 series toilet.

Thanks in advance.