Yes, you can claim these eligible medical expenses. Once you enter a T4A with Box 135, the software will automatically post the amount to your medical expense profile. Do not enter this amount twice 🙂
If you missed claiming this amount in prior years, you will need to make an adjustment to each of the missed years. An adjustment can be made online if you are signed up for CRA's My Account Service, or by completing the following form;
https://www.canada.ca/en/revenue-agency/services/forms-publications/forms/t1-adj.html and sending to your Tax Services Office.