If its a new thread, the pictures are stored on your phone or pc and you are not a replying to a thread I believe the easiest way is to:
- Click on Attachments (paperclip icon)
- in the Manage Attachtments window under the Upload File from your Computer click on the Browse button
- Locate the pictures
- Select pictures
- Click on the Upload button
- Close the Manage Attachments window
- Your pictures will not appear until after you click Submit New Thread
The other way is to use your Google+ account or Photobucket or whatever service you use to store pictures and follow what Mahigeer said or you can just get the tapatalk app and be a geek like Momofish