See
http://office.microsoft.com/en-us/language-packs/ for information on how to get an English Language Pack or Language Interface Pack. While the version you got may have English proofing
tools, in order to get English for the UI (Ribbon, menus, dialogs, etc.), you will need a Language Pack or LIP. If you determine that you need the English Language Pack, select English from the dropdown, and you will be given the opportunity to buy it (in
the U.S., the cost of each LP is $24.99; I don't know how much it would be in Bhutan). Alternatively, you can get proofing tools and ScreenTips free.