Two ways to stitch invisible zippers​

You can stitch an invisible zipper using a regular zipper foot. A conventional zipper food is a standard presser foot included with your basic machine set. These presser feet are very narrow aligning the machine needle to either the right or the left of the foot plate. A zipper foot is used to stitch next to zipper feed, decorative elements, raised edges and other obstacles you'll need to stitch next to in the dressmaking process. The location of the needle in relation to the plate is chosen based on the direction in which your sewing and the raised edges you are stitching against.
When sewing an invisible zipper, the needle should be aligned such that it stitches in the crease created by the zipper folded zipper teeth. When using a regular zipper foot, you will have to unfold the zipper tape and hold the coils up. Doing so will help the foot plate align the needle against the coils, guiding it smoothly along the zipper tape crease. 

If using a regular zipper foot it helps to hand baste the zipper tape to the garment's seam edge so that the zipper does not shift out of alignment as you keep the zipper coils up. 

The easiest way to stitch an invisible zipper is by using a specialized invisible zipper foot. While an invisible zipper foot will most likely not be provided with your machine set, you can purchase one individually based on your machine model. This unique zipper foot has one or two slots (usually two) that keep the coils  continuously pointed upwards as the stitch is applied right next to the zipper teeth, in the crease created by the folded tape. You might have some difficulty inserting the beginning of the zipper coils into the slot, but once aligned, the narrow slots are able to keep the zipper teeth perfectly in place minimizing the risk of stitching unevenly.