Your GST/HST return would be separate from your income tax and can be done through the CRA.

There are currently three ways to register for a GST/HST number- you can do it online, by telephone or via mail/fax.

More details from the CRA can be found by visiting: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/gst-hst-businesses/register-a...