Open the Photos app
Tap the photo or videos you want to delete
Tap the trash icon
Tap Delete Photo or Delete Video
Open the Albums tab
Scroll down and tap Recently Deleted
Tap Select
Tap Delete All or choose specific items
Tap Delete to confirm
Go to Settings
Tap Photos
Turn off iCloud Photos if you do not want deleted items synced across devices
Delete photos from iCloud.com if they were synced to iCloud
Empty the Recently Deleted album on all synced devices if needed