Hey Rod, been there done that.
When I got my first harp, it came with a complete set of nylon replacements–and no labels. So we got to play the guessing game. We also didn’t know how to change the string. Hello, internet.
Unfortunately, changing a string is like riding a horse: if you have no experience, then someone’s going to get hurt.
I suggest either a) asking your teacher to show you how to tie and change a string or b) ask a sympathetic harpist in your area. It’s easiest if seen done.
Also, when I first changed my first string, since I didn’t know how to do it, we did it