Where do I input my ITCs (Input Tax Credits) to reclaim the GST/HST paid out on purchases used for re-sale that were exported to the USA?

If you are Self-Employed and a GST/HST Registrant, you do not include any GST/HST you may have collected or paid out in ITCs on your T1 General Income Tax Return. Registrants should keep all GST/HST collected on income and paid on expenses separately from the T2125 Business Statement on their personal tax return, and complete a GST/HST Return instead.

https://www.canada.ca/en/services/taxes/gsthst/gsthst-returns.html