How do I post a photo on Instagram?
To upload a photo or take a new one, first tap 
- To upload a photo from your phone's library, select the photo you'd like to share.
- To take a new photo, tap
above your phone's library. You can tap
to switch between front and rear-facing cameras and
to adjust flash.
Once you've taken or uploaded a photo, you can add effects or filters, a caption and your location before posting. You can also post a video.
Note: You can't take or upload photos from a desktop computer.