how do i go back and put a phonto on here when i do it only gives option of photos that are not on here jusy empty

If you're using the Android app:
- Tap on the little circle with a "+" in it at the right bottom corner of an empty photo
- Select "Browse album" and choose a pic from your album
or
- Select "Import from Facebook" ...

what if that doesn't work

Generally, when asking for help about something technical, the question works best if you specify exactly
- what you are trying to achieve
- the steps you performed
- what happened
in detail.

"Doesn't work" is too less information.

can't post a photos