Look up pictures of the android interface online and find the language settings. The skins can be different, but just navigate the icons until you find settings, and from there, look for an icon that might be language settings. Finally, just pick your language (they read in the language of the speaker) and bam, you're done.
All android tablets may have varied icons and whatnot, so I can only give general instructions on what to look for; the process is easy however. I have to reset tablets from Chinese to English all the time at work because they're too ignorant to set it back when they change it.