Need Help with Opening Maps

I have a huge problem. I want to edit one of the Blizzard maps (Plunder Isle), but when I open the map it opens it with the normal world editor. I want to open it with Unswe. How would i do this?

You load it from within UMSWE, that's not soooo hard to figure out.

If you´re reffering to "double click on any W3M" and open it on UMSWE this is not possible. Just run UMSWE and then go to the menu File->Open....