Making a invisible zipper is easy to do when you know all the tricks. I will here try to share all my tricks and hopefully this will help you to do it yourself.
All you need:
One invisible zipper
The best tricks when you are sewing is to check of it is like you want it to be before you sew. This is very easy to forget. Pin it like you wish it to be and check if it is correct.
Lay the zipper as you wish for it to lay when it gone:
Fold out the zipper and pin the zipper to the fabric
Sew inside the fold in the zipper. Use a zipper foot on the sewing machine if you have it, this makes the sewing much easier.
Do not sew all the way down, leave ca 5 cm.
Zip the zipper all the way up and mark of where the zipper meets folds in the garment. You wish the folds to meet in the same spot when you are done.
Pin the zipper inside the fold to the other side. Remember to check so it is right!
Sew in the fold in the zipper.
Sew together the fabric in the hole in the end of the zipper.
Voila! Your done!