Page setup
Menu/Format/Page - Page - Orientation.
If you need different Orientation in other sheets, there is needed to create another page style, an apply to the sheet.
Actually it makes more sense that Formatting a Page is in the Format menu and not the File menu (as Microsoft as always included). In the File menu should be operations that refer to Files (e.g. Open, Save, Print). In fact, File Exit doesn’t even make sense. You don’t Exit from the File, you can Close a File and then Exit the Program (or Close it, Unload it, whatever)