Restetting Mozilla so I uses English

[textbook]

My Mozilla fox settings are set for another foreign language, how do i set them for English?

 

[PC Hobbyist]

I don't know if you have to reinstall firefox in the version for the desired language:
http://www.mozilla.com/en-US/firefox/all.html

Or if what you mean is the language display for webpages.
Tools >> Options >> Advanced tab >>General tab >> Edit languages