We all have to start sometime! No question is silly, so I'll try my blonde best to answer--
Divided refers generally to the fact that there is an amount of an ingredient needed for the recipe (i.e. 1 cup of sugar), but perhaps 1/3 of it is at the beginning and the rest gets added in later in the recipe--thus you divide the 1 cup into 1/3 and 2/3 cups. I hope this makes sense.
Prepared mustard is powdered mustard and comes in a can where the spices are.
Crushed pepper flakes are also in the spice section--think of the peppers that are on the table when you get pizza or spaghetti out--that is what they are referring to. It will be in a spice jar.
I hope this helps and that I haven't confused you! Good luck, and enjoy!
Bonnie