Thanks for trying to help but you seem to miss out all the critical (difficult) steps. I have read the guide and still have no better idea of what to do.

How do you secure the new zipper?

Where is the zipper stopper? how did you remove it?How do you reattach it? How did you get the new zipper slider on?

How do you get access to the end of the slider chain?

You have highlighted the zipper slider but say to remove the metal stopper. What do you mean?