How can I get a phone app on a tablet?
If you already have the app on your phone, you might want to take a look at AppMonster. This app allows you to create backups of your apps' .apk files to your SD card (the Pro version even can do so automatically each time you install/update an app, so you always have the chance to revert to a previous version if an update breaks something). You can then pick that .apk from your SD card, copy it to your tablet, and "side-load" it (i.e. install it manually). For this to work, you must enable "unknown sources" in your tablet's settings (otherwise it only accepts installs directly via the Playstore).