I need to add a tracking code to my forum. In the past I've done this by going under Admin->Appearance->Customization->Themes and then editing the globalTemplate template. But I just tried this again but can't find where I access this template. Can you please help?

You could use ACP => System => Integrations => Google Analytics 

integration to add literally any analytics code, not only Google 🙂

 

Or on the themes site, edit the theme. There, we have now 2 fields where you can add custom code at the beginning or end of the body tag.