How to add custom dictionary for word

[seghwa]

I am living in a place where learn British English as second language. So, I often encounter one problem when using Microsoft Word. When I use the spelling check, it always says spelling error on certain word like "travelling". It is because word is using the US Dictionary. It has the option to choose a custom dictionary.

So I am asking did someone know where can I find this British or UK custom dictionary for Word?

Thanks in advance.