1. Save the photo to your local drive.
2. When you are creating your post, after typing in the text, then choose the button for Manage Attachments
3. Click the Browse buttons to locate/select the individual photos
4. Click the Upload button
5. Click Close this window in the top right corner
6. Click the Submit button
After you upload the photo(s) from your local drive, you can delete them.
Alternatively, if you have a public accessible link to the photos, just click the photo widget from the message post toolbar and enter the link in the popup you get.