Good evening Cornelia and welcome to the Events Calendar Support forum!
Thank you for reaching out to us.
I would love to help you with this topic.
You have found the perfect article to do what you are trying to achieve.
The answer to your question (where to put the code) will largely depend on what views or widgets you are planning to use (monthly, weekly, etc.).
I believe that you are either going to use the weekly view or the weekly view widget (based on your description).
Either way, you might want to read our Themer’s guide to get a sense of how that works.
Simply put, you can make a copy of the view you want to tweak to your /tribe-events/ folder and add the code there.
Just to set expectations, as you might know, the scope of our support is mostly to get our customers started on the right track and to help them in case of issues. We unfortunately do not provide complete support for customization.
Let me know if that helps to get you started.
Best regards,
Geoff B.