you put your quilt top face up on the floor - then you put your backing face down on top of the quilt top. Then you put your batting on top (if you are using battting)
then you sew all around the edges of quilt (about 1/4") but leave about a 6" opening (or whatever size you feel you need - bigger quilts and more batting may need a larger opening)
then you reach and pull everything out that opening. Then you sew around the edges again and sew the opening shut
this video isn't an instructional video - but it shows the turning the quilt right side out
https://www.youtube.com/watch?v=nroeCv904NQ