Is your document a Word Processing document, or a Page Layout document?
Click on the Document button, then look for the Document Body checkbox. If it is checked, you are working with a Word Processing document, and you should find an invisible character (most likely a paragraph break, a page break or a section break) causing the second page to appear.
Deleting that character should make the empty second page disappear.
If the box is not checked, you are working with a Page Layout document.
In a Page Layout document, every page is a separate section.
Click on the View button to open the left sidebar and show the page thumbnails of your document's pages.
Click on the empty page, then check that the yellow rectangle that appears contains ONLY that page. Having confirmed that, press delete to delete the selected page.
Regards,
Barry