How to merge subdirectory

I recently got a Sub-directory for non-English speakers for my site. I’d like to merge this onto my main site but having difficulty with this. Some mentioned that it would be easily be done via mydomain.com, but I was wondering if there’s any way of doing this within WordPress as I’m not too keen on having another account and pay additional fee unless absolutely necessary. I thought I’d try my luck and see if anyone could advice me before I process with signing up with mydomain.com.

Any useful tips would be greatly appreciated!

-Mari