@twowheels,
@geek1011's solution is the most flexible long-term if you're planning to install several custom dictionaries. But, if you're just looking for a quick way to add a second English dictionary, with minimal effort and no learning curve, this may suffice:
- rename geek1011's dicthtml-wb.zip to dicthtml-en-en.zip
- drag-drop it to the \.kobo\dict directory
- reboot
That should give you an extra dictionary, labelled 'English - English', in your dictionary drop-down list. The Kobo default dictionary will still be there as 'English'.