T-shirt Mock Up

[gimpstudent]

Hey everyone, this is my first post here and I'm hoping for some advice.. Months ago I downloaded a t-shirt mock up template to post online, I have tried many tutorials written and on Youtube over months to try and figure out how to actually get the t-shirt to show up, I just cannot figure it out. I'm running out of ideas how to figure this out anymore so thought I'd ask here.. Any ideas or a direction to point me in would be much appreciated.

I have attatched a screenshot