It depends on what type of therapist you are seeing and which province you live in if you are eligible to claim these expenses. Here's the list from CRA detailing which Medical Practitioners by Province you can claim medical expenses for: https://bit.ly/2nuFp8U

You can enter these expenses in under the Medical Expense Profile as you would any other expense. Go to Deductions > Medical Expense Profile > check Medical Expenses 2018 > continue to the page that allows you to Enter New Medical Expense.