Step One. Save the image on your iPhone.
If you took the image with your camera, then you are all set. If it was emailed to you or messaged to you, you must save it to your phone. This example shows how to save an email attachment.
Click on the photo in your email. You will see a little box with an arrow in the bottom left corner. Tap that.
Step Two - Select Your Facebook Profile Photo
Open the Facebook App on your iPhone. Click on your photo in the newsfeed. Don't click on the Story icon.
You will be taken to your profile Screen. Click on the little Edit bottom on your profile photo.
You are almost done. Look at the photo in the square. If you don't like how it fits in the square click edit.