It depends how your document is set up, but it's not a problem. To start with, for a 4 page document, I wouldn't use facing pages. My own preference is to create a double-sided sheet, so your document is twice as wide as it should be. Just tell your printer to fold it in half when it's printed.
If you need to create a 4 page document though, go to View > Show Document Layout. In the palette that appears, drag the pages beside one another, so you have two spreads.
Either way, you can see the entire spread, and you should be able to create a text box that extends over both pages.