Open the Google Photos app or go to photos.google.com
Sign in to your Google account if needed
Find the photo you want to delete
Tap or click the photo to open it
Select the Delete or Trash icon
Confirm the deletion
Empty the Trash if you want to remove it permanently
On mobile, you can also press and hold the photo, then tap Delete
On desktop, you can also right-click the photo and choose Delete
If the photo is backed up on another device, delete it there too if needed