As far as I know, it’s impossible to have horizontal text and vertical text on the same page of a Word document — at least not in a useful sense. You’ll need to have the table on a page by itself. To do this, insert Section Breaks (Next Page) immediately before and after the table (i.e., before and after the table and any associated titles or captions that you want to appear with the table). Do this by going to the “Page Layout” tab, “Page Setup” panel, click on “Breaks”, and select “Next Page” from the bottom part of the menu that pops up. Then click somewhere in the page with the table on it, and (also in the “Page Setup” panel) click on “Orientation” and select “Landscape”.
Note: These instructions are based on Word 2007 / Word 2013 on Windows.