The T2125 is for, Statement of Business or Professional Activities, to report your business and professional income and expenses.
You can claim CAA on your rental unit under Income- Rental Property- Continue (If you are using the Online version and if you are using Download version you will need to go to Easy steps). You might now need to click on Edit the continue, and on the next page you will see the "Rental Profile" make sure you check off the last one which says "Calculation of CCA Claim". Then continue and you should see the page which allows you to enter your CCA amounts.