If you ask, you have always to inform us:
And a screen shot and description what you have done would be helpful.
You should not put a text frame on the mast except for placeholders like page numbers or if you are using InDesign CS5 and later, primary text frames.
You can use layout adjustment when you change page margins, BUT you must have designed correctly. Layout adjustment works only with frames which are strictly aligned with the margin guides and also to other guides. Free floating frames will not be affects.
I own In-design CS6
I went to Layout > margins and columns and that may provide a method of altering the size of the text box.
How would I use layout adjustment? Would that involve going to Layout > Margins and Columns or did you have a different method in mind?
Thank you for your help
In CS6 layout Adjustment is hidden under the flyout menu in the Liquid Layout panel. It must be turned ON before you make any changes to margins or frames if you want it to work.
In this case, the first step, after turning on Layout Adjustment, would be to go to the master page and adjust the margins to match your text frame, if they don't already, then adjust them to the new dimensions.
Even overridden frames should now move with the margin adjustment, as long as they were snapped to the margins before they were changed.
I turned on Enable Layout Adjustment from the Liquid Layout panel but I'm still unable to select the master pages text box.
After turning on liquid layout I get the following warning message from the Liquid Layout panel:
Liquid layout rules do not apply because layout adjustment is enabled for the document. Click to disable layout adjustment.
Waht do you mean you are unable to select the master pages text block? Are you on the master page?
Of course, there is no reason you should want to select it at this particular point. You want to make the margins match its dimensions, not the other way around, if you expect the frames on your document pages to be adjusted.