Hi JudithJeanne. Welcome to the group. A .cbz file is simply a collection of jpegs. Most of the files on cb+ are in that format. If you download them to read on a pc, install a programme such as CDisplayex, which will open the file and let you read them away from this site. If you want to read on an android device, install on your tablet a programme such as perfectviewer, which is free on Google store.
If you use Macs, someone else will have to help you out.
Good luck and enjoy the huge selection of books we have here.