If, like us, you're a bit lazy, you'll ask the author to create as many files as the number of frames needed. But the trouble is that the author might be as lazy as you are and he or she might not know more than you about how much text should be imported into each frame. So the problem still prevails. In fact, a layout program can simulate some kind of text processor behavior in which the text flows from a frame to another. This is done by linking.
Linking is done with the Link Text Frames tool (N) or can be set at the creation of the document. The use of one method or the other depends of the layout type that you're creating. As often, you can use the following menus or icons to link or unlink:
Item | Link Text Frame or Item | Unlink Text Frame menu
In the toolbar, the following icons link
and unlink 
What you need to remember is that you need to use the Link Text Frames tool comfortably:
You need to select the frame in which the text is actually placed...