In the form "Work-Space-In-The-Home Expenses", do I need to enter the same amount in the GST,HST,Zero Rated & Exempt ? or just in one box?

No, you would put the full amount of the expense in just the box for whatever sales tax you paid on it. ex: If you paid GST on an expense, you would put the entire amount (cost+GST) in the GST box.

Thank you.  What is the zero rated box for?  For amount paid without taxes?

Yes, it's for amounts that don't have sales tax or are zero-rated.