But the question is, assuming you are trying, perfectly reasonably, to change MEP's default folder settings, have you already created the "new" folders before you attempt to make the changes you want?
If you follow Carl's advice in the first reply to your question and look carefully at his screenshot, on the "Browse for folder" screen there is an option, lower left corner, to "Make New Folder". If you click this and then rename this "New Folder" to whatever you want it to be, can you not then select it as one of the destinations in your Settings screen?