I originally "Scanned" my signature and saved it as a .jpg file, then using word I created a default template with the signature set to "move with text"
Now each time I open word, it automatically contains the signature.
If you don't want to do as above, then you will need to "Import Picture" each time you want it in place.
However this will not work with "Notepad" (not sure about Wordpad, but it should work also)