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Really???
Check THIS!!!!

Well, if it's me i will use Use Case and Architecture Diagram in this case.

So, you must focus on Architecture Diagram for now.

Exactly, it's a little clear for now.

She is true, you must break these two cases into sub cases to elaborate it further. Like,
1. Set Preferences.
i. By Categories
ii. ...

And you didn't bother to extract anymore? You must ask the person who gave you this description, to elaborate it more.

I can just say Good Luck. You were not so descriptive. Sorry.