Learn the steps by watching the video tutorial below.
Even out the edges then secure it with pins, then sew it.
fire up the zipper and sew the remaining part.

Image credits: AmyFamily DIY via Youtube
Unfold the fabric and iron it in the needed position.
After this, make another stitch, two to three millimeters away from the edge.
(This would prevent the fabric from getting stuck in the zipper while using it.)

Even out the edges, secure it with pins, then sew it.
Unfold the fabric, iron it again in the required position, and sew it.
(The zipper blade should be facing the inside fabric.)

Fix this in this position and secure it with clips.
Secure the perimeter with pins.
Leave a gap in the inner fabric to turn the pouch inside out later.
Sew along the perimeter, ignoring the gap.
After sewing, cut off the corners.
Do the same on all four corners.
Sew all four corners along these lines.
After this, turn the pouch inside out, then sew the gap close.
Your pouch is now ready.