Where can i find the rent expense ( line 229 ) for form T777 in the software, is it the office rental section? and Does it count as zero - exempt gst/hst ?

You can find Employment Expenses in the lefthand navigation bar under Income > Employment Expenses. Alternatively, you can click on Find in the upper right and type in "Employment Expenses."

And yes, it is zero-rated/exempt.

Note: You will need a T2200 form from your employer to be able to claim these expenses.