I would like to categorize my recipes as I add them, plus ones that I have already added. When I select categorize a screen comes up but will not let me enter anything and the selection just says "none".
First you need to add categories to a cookbook. Then you can assign those categories to recipes. See Topic 148 and then follow Topic 146 on this web page:
This is covered in the program's Help section too. Select Help Contents from the Help menu in MasterCook 14 on the computer.