Welcome to the community!
If your new phone uses the same sized SIM card, you should be able to take the SIM card from your old phone and place it in your new phone. On the other hand, if you require a different sized SIM card, you might need to get a new SIM card. If you purchased the device from Fido, I believe it would come with a SIM card. If you do need to use the new SIM card, you would need to update the SIM card information on your account via your My Account. From the Account Overview page --> View Usage & Manage. On your Dashboard, the option to Update SIM card would be under Quick Actions, near the bottom of the page.
Hope this helps 😀