: Apply double-sided basting tape to the zipper tape to hold it in place against the fabric before sewing.
To secure a very long zipper into a project without it puckering or shifting: ShadyLewds_Collection_2019.zip
Slide the longer side of the tape into the pull first, then guide the shorter side in. : Apply double-sided basting tape to the zipper
If you have raw zipper tape and need to attach the pull/head to create a functional long piece: Add Zipper Pull on Raw End of Tape
To give you more specific advice, are you working on a (like a jacket) or a large gear project (like a tent or bag)? Add Zipper Pull on Raw End of Tape Tutorial
: For very long items like parkas or sleeping bags, you can install two sliders. Slide the first one down so it is flush with the second, allowing the "piece" to be opened from both the top and bottom.