Elizabeth am I right in thinking you want to offer free local pick up?
If that is the case then you don't need a discount code. Just go to shipping and create a new shipping profile, stating local pick up.
https://help.tictail.com/hc/en-us/articles/205534661-Setting-up-your-shipping-options 8. When writing your free pick-up title, make sure it's clear to the shopper that they will need to physically pick up their order. As for additional information, you might want to let them know how they will know when their order is ready for pick-up. Lastly, remember to give the shopper the pick up address so they'll know where they can get their order.