How do I cut a bigger model into pieces to print separately and later stick together?

First of all, CraftWare is a slicer program and not a design program. However, if you have an object that is too tall to fit in your build area, but not too wide, you can pick a layer in the middle of the print and drag it down through the virtual buildplate.  Then make a second print sceme flipping the object upside down and dividing it with the buildplate along or near the same middle layer selected previously.  After printing, you can attach the two pieces to make a larger print.

But really, we best recommend that you use a design program. Here’s a good one: