Hi there brenda-moore,
It's important that all your transactions have the correct tax so you know the correct amount owed to the federal and provincial governments. QuickBooks Online is a great tool able to keep track of sales and expenses so you know the profit of your company. I can point you in the right direction to where you can set up your sales tax.
Go to the Taxes section, then manage Sales tax. Select the option to add a tax, then choose to start tracking in a new province. Choose the province which you'd like to add, then repeat for the other provinces.
if you have any other questions, feel free to reach out here.