How do I paste formatted text into text frames on master pages?

Dear Forum.

I have started a 200 pages document the wrong way, and need a tip how to fix the damage. Silly me :

I had not prepared the master pages with text frames but just placed the text in reflowing frames in the document.

Now it is of course difficult to resize frames and pages and I would like to add text frames to my master pages.

But no matter what, the original text frames follow along, I can't get rid of them. They just stay on top of everything.

So, could anyone please tell me how to cut the text from my document and past it into the textframes on the master pages and make them flow nicely through the document (which has the same margins etc.)?

P.S. I can't start all over because lots of corrections have been done already.