To do this in TurboTax Online, please click on Find (magnifying glass) in the top right-hand corner. Type "union" in the box, then select "Union or Professional Dues" from the list and click “Go”. 

Thanks for your reply. I was however looking specifically for the deductibility of the licence and application fees. These are different costs than the annual renewal of the membership fees.

@RobertW54 Yes, if you are a registered nurse in Ontario, you can likely deduct your Ontario Nursing License fee (CNO fees) as a professional membership fee on your tax return, provided it's required to maintain your professional status recognized by law We would suggest contacting CRA directly to get more information.