Use the Story Editor?

The Story Editor can be selected by Right-clicking in your text frame and choosing Edit in Story Editor from the menu. The reason this exists is so that you can edit large chunks of text in a simple text-only format, much like an old word processor. Just place the cursor anywhere in the text and you can start making changes or additions to your text without worrying about frame sizes or pages. This is especially useful when you’re working with linked or threaded text (see page 105 for how to link text boxes).