If I select office in home expenses, should I select designated workspace (room) and only fill up workspace rent as "type of expense" on the "expenses which you incurred for office space only" section and the amount of expense on the "zero rated & expense" column?
No. You would have to figure out what portion of your room that you use for work - this generally would not include the kitchen, bathroom, laundry or sleeping areas.
You would enter your expenses in the GST, the HST or exempt/zero rated column depending on what tax you paid.
I am will allocate the home rent coz I am using half of the room as office and half of the room as bedroom.
I am not paying any utilities coz it is all included in the rent. How should I claim this?
If your utilities are part of the rent, then you are claiming them when you claim your rent. You can't claim them separately unless you are paying for them separately.
So does this mean, i can select designated workspace (room) and only fill up workspace rent as "type of expense" on the "expenses which you incurred for office space only" section and the amount of expense on the "zero rated & expense" column?
If you enter you rent under "Expenses which you incurred for the entire home", then TurboTax will automatically calculate the amount of rent that you can claim, based on the area of the space used for business and how much you work in there. The "expenses which you incurred for office space only" section is for things you pay for that are just for your work area, ex: ink & paper for a printer you only use for work.
You can enter your rent under the "zero rated & expense" column if you didn't pay any sales tax on the rent.