Hi, initially you need heat, either a heat gun or hair dryer. Adjust the front hooks all the way out and if that's still not enough gently heat the roof at the stretch points, the hoops, (don't get to close) you will need a second person to help to keep pulling the roof GENTLY.
Don't rush! If and when you get the roof closed wet the roof toughly using warm water and a sponge and let it dry slowly. this will evenly stretch the fabric.
Don't try to force it closed as this can cause damage, you can pull the rear window seam, damage stitching or dislodge the butyl seal on the rear bulk head.
This tip was given to me by a soft top fitter.
Don't forget to re-adjust the hooks once its all stretched out
Hope you get it sorted