Click on "Go advanced" and then click on the paperclip. Then click on "add files" and then click on "select files". Select the files that you want then click on "upload files" and then "insert inline".
Yes, there is a threshold number, unspecified to defeat spammers. Utahrocketpro, welcome. Stick around for a few days and post in interested threads or the word association thread in the Watering Hole and you will have completed the "double secret initiation".