@Barb Binder makes another very good point about determining where a frame is located, but it is a subtle detail.
If you don't understand how Parent pages (formerly and still often referred to as "Master" pages) work as an underlying design element, you're going to have a lot of hurdles in trying to edit documents in InDesign. It's not like Word where (generally) you can just plow along; you HAVE to know a spectrum of basic structure and design elements to even begin using it effectively. This is true even with templates to guide you — maybe even more so, since you have to unravel how the original designer built the model. There are few templates where you can just open them, edit a little text and have a desired result.
You might benefit from some of the basic tutorials, to get you oriented with ID's features — such as this one: https://helpx.adobe.com/indesign/using/parent-pages.html