Make sure there’s text on it and select the text. Open an MS Word document and go to the page you want to change the orientation for. You can set a different orientation for any page within a document if you know which option to use. There is no option to change the page orientation for a single page in MS Word, at least not an obvious one.
You can change the orientation any time you want but it applies to every single page in a document.
MS Word lets you create documents with pages that are in landscape or portrait view.