I completely understand mate, no problem. It should automatically create a vmt file as well. Should go like this:
First of all, translation because my OS is in Portuguese (my language): Guardar = Save, Os Meus Documentos = My Documents, Abrir com... = Open with..., Escolher programa = Choose program
Open the image you want to make a spray of with VTFEdit.
Press Ok.
Go to the File tab and press Save.
Type the name of the file you want where "yournamehere" is. then Press Save and that's it!
The .vtf and .vmt files are surrounded by a black box. It was assembled in MS Paint in a hurry, sorry for that.
If it is not working this way, then unfortunately I don't know what is the matter. You'll have to consult the author's website to figure out a solution. In the meantime, if you need that spray bad, attach the file that I'll convert it and then post back here.