@Tahereh1 I have added my GST number and info in my Airbnb tax settings and the 5% gets added to each booking and paid out to me to remit.
I can't remember if I added a setting somewhere that it's a 5% tax.
If you are under the Canadian threshold for income subject to GST, then you don't worry about it. I had an existing GST number for my work already, so just added it to the Airbnb listing.
If you're income from Airbnb will exceed the Canadian threshold, you'll have to apply to get a GST number and make remittances.
The good news is that you're accountant should be able to make claims against it for the GST you've paid for supplies, repairs and services at your rental. Make sure to ask your accountant though, I'm not a tax advisor!
Hope that helps.