Landscape orientation for games.

Whether those games will work in landscape orientation will depend upon how they are coded, they may only work in portrait.

If you are on your iPad's homescreen then does the screen rotate if you turn the iPad ? If it doesn't then is there a lock symbol at the top of the screen next to the battery indicator ? If there is, then depending on what you've got Settings > General > Use Side Switch To set to (rotation lock or mute notifications), then you can lock/unlock the rotation by the switch on the right hand side of the iPad above the volume switch, or via the taskbar : double-click the home button; slide from the left; and it's the icon far left; press home again to exit the taskbar. The function that isn't on the side switch is set via the taskbar instead : http://support.apple.com/kb/HT4085

If there isn't a lock symbol then try a reset : press and hold both the sleep and home buttons for about 10 to 15 seconds (ignore the red slider), after which the Apple logo should appear - you won't lose any content, it's the iPad equivalent of a reboot.

In addition to what King_Penquin said, not all apps are made to work in both orientations and this is especially true of games. That said, if made to work in one orientation or the other, the app will default to that whether the orientation lock is set or not.

You're welcome. Have fun!