If using Desktop, click HERE.
If using Mobile Web (Not the App), click HERE.
To add a photo to a post you are creating....
Log into your account and click the "Home Page" button.
Click "Add Photo" and select either "Take Photo or Video" or "Photo Library" to choose the photo you want to attach.
After taking or selecting your desired photo, click "Share".
Once you've clicked "Share" you will see your post beneath the "All Activity" bar.
Now that you know how to add a photo to your post, head over to the site and give it a try by clicking HERE.