Well.

Perhaps the best thing to do is to learn all those methods separately first, so that you can combine them and get the desired result.

learn how to add text to a GIMP file here.

learn how to apply text to a path here. (There are 2 methods in this tut. Only the second one is really useful - the way I do my own curved text)

Adding spaces between letters is as simple as hitting the space bar between each letter as you just type them in (remembering to type the same number of spaces around each of the spaces themselves, or your words will run into one another

EDIT: and I'm so sloooooooooow at watching vids to check their ok and say what they need to that I've absolutely missed the boat LOL!