Can someone guide me here?
I need to remove the text saying 'Burn the fat guarentee' To put my own. Can someone teach me how to do this?

What the reason for this "need"? Class project or to use for your own? You'd gain more experience trying to remake something like that than trying to modify one that's already made.

Well its for a freelancing site but I did not get selected so thats why I want to just for the sake of it know how to do it.

In order to remove the text, you require the pen tool, the eyedrop tool, the gradient tool and the text tool. The eyedrop tool for selecting the two main colors in the gradient; the dark and light ones; one taking the place of the foreground color and the other taking the place of the background color. The pen tool for tracing around the part of the ribbon that has the text. After tracing, you convert the path to selection, then fill the selection with the gradient tool with the bi-linear effect (i think it's what it's called). In Photoshop, you can create a path, and with the text tool write on that path.

I would just remake the whole thing. Then you can change anything else you might not like, or you can add something you think is missing to make it look better. I think that would be easiest, smartest, and most rewarding.

meh add your text