I've never added a zipper before and this Debbie Bliss pattern just states "add zipper". Anything I should be aware of while sewing in the zipper?
Measure the length of zipper you need without stretching out the knit piece. You don't want the zipper to be too long. Slightly too short is better than too long. I pin one side of the closed zipper near the edge and then fold the other edge so that the two knit edges abut. Then I pin the second side. It's worth it to baste the zipper in place and make sure it's right before stitching it in place.
Finally, I almost never succeed the fist time I baste the zipper in. I sigh and promise myself that I'll give it 2 more tries and if it doesn't work, I'll take it to my LYS. It has always worked on the next try. Good luck to you!