This collaborative gallery is mainly for everyone who has downloaded the app to be able to post pictures to the app from their phone. But, if you want to add pictures from the computer, you can by clicking the camera icon in the upper right corner.
To add photos from your phone, tap the camera icon in the upper left corner of your device, then take a photo or choose one from your images library.
If you want to delete something that someone posted to Crowd Pics, head to the right panel in your editor. You can click the 'x' in the corner of any photo to get rid of it.
You can also choose who can upload the pictures. If you keep "Everyone" selected, anyone who downloads the app can put in pictures. If you choose "Admin Only", you'll be the only one who can add pictures from your phone.