Adding text to a section

Hi - having set up various Sections across the desktop of my prototype website, I want to add text to each section that reminas inside that sction and describes the function of that section, how it links to other sections etc. However the text box I’ve added, although nested under the resepective Section layer, can be scaled and moved outside the boundary of that Section. I notice on the pages that come already set up as examples on the Getting Started page, the text boxes are constrained by blue dotted lines. I can’t find reference to setting up these constraints in the Help notes. Great if someone can direct me to the relevant Help notes. Thanks, Richard