To separate two words, you have to manually add a space to the closest word when creating the song in your editor.
There are two ways of doing this: adding a space before the next word starts (A) and after a word ends (B):
(http://i.imgur.com/zvGXV.png)
According to the USDX documentation, the recommended way of doing it is A (before each word) so I'd advice to use this. It also makes things easier to read when opening the raw txt file. ;)