They are easy enough to delete directly from your iPhone.
Open up your Photos app on the phone & indicate the “Album” that contains the files you want to delete.
Tap the blue Select in the upper right-hand corner. Then select the photos, videos, etc. you want to delete by tapping the thumbnails; there will be a little blue checkmark in the lower right-hand corner of the image.
Now press the blue icon of the trash can in the lower right-hand corner of the screen. A bar will raise from the bottom of the screen with an option to Delete Photo or Cancel.
Press Delete Photo. Your selected files will now be moved to the album entitled “Recently Delected” where they will reside for for up to 40 days (in case you wish to retreive them). If you’re sure you don’t want them and wish to free up spoace on your phone immediately, again press the blue Select in the upper right-hand corner of the screen. Then press the Delete All button in the lower left-hand corner.
Confirm you wish to delete and BAM . . . they’re gone!
Hope this helps! 
