You can add a photo to a post through the following steps.
■Steps (For iOS and Android)
1. Tap on the icon at the bottom right of the timeline or profile screen
2. Tap the Photo icon on the bottom left
3. Select the photo or video you would like to post
4. Tap Attach at the top left for iOS or Complete at the bottom right for Android
You can post up to 9 photos
You can post a video of up to 3 minutes
*If the video is longer than 3 minutes, you can trim it inside of Yay!