You can go to your Profile, tap on your Story, swipe up on the Snap you need to delete, then the trash symbol will appear, or tap on the three-dot menu on a Snap and choose the Delete option.
How to delete a Snap story easily:
Just open Snapchat, tap your profile icon, and go to "My Story." Find the snap you want to delete, tap it, then tap the three dots (⋮) or swipe up and tap the trash icon. Confirm, and it’s gone!