Hi there JANECCC1,
it's important that all your information be correctly entered for your taxes to be correctly filed. The Pro Tax tool in QuickBooks Online Accountant is a great tool able to help streamline the process of creating and filing tax returns based on your client's books. I can point you in the right direction for information about Web access codes.
When creating the filing, you can enter your Web access code, or leave it blank for it to be generated based on the CRA. That information can be viewed in this article.
If you have any other questions, feel free to reach out here.