It's great to have you here in the Community, @allan20!

To add GST to your products or services, you need to enable it first. Doing so will also allow you to lodge your business activity statement (BAS). I'd be pleased to guide you through the process. 

Here's how:

1. Go to the GST menu and click Get started.
2. Under the GST section, choose the accounting method and BAS lodgement frequency that applies to your business. If you're not sure which option to choose, you can get in touch with your accountant or bookkeeper, or contact the ATO.
3. If your business is obligated to report Pay-as-you-go Withholding, select the PAYG Withholding box to "tick" it, then choose your reporting frequency.
4. If your business is required to report PAYG Instalments, select the PAYG Instalments box to "tick" it, then choose your reporting method and reporting frequency. You can also visit the ATO website for more information about the reporting method.
5. If you report any of the following taxes, select Other taxes and tick the ones that apply to your business:
   • Fringe Benefits Tax
   • Fuel Tax Credits
   • Wine Equalisation Tax
   • Luxury Car Tax
6. Click Save and finish.

Now that you're set up for BAS and GST, you can start recording transactions with GST in QuickBooks Online (QBO). For more detailed information, feel free to visit this article: Set up GST and BAS in QuickBooks Online.

Just in case you want to edit the GST settings, you can check out this article for guidance: Edit GST settings in QuickBooks Online.

If you need further assistance setting up your GST, please don't hesitate to reply. I'm still ready to help you out.