If it doesn't work, once you're at the clan page. Click on playstation clan, or Xbox clan, depending on your console. It says it at the top of your clan name. After that an option that says “Group Wall" will appear on the left of where it says “Group Forum" click on “Group Wall" Then once you're at that page, at the very bottom will be a text box, write anything down on it then click submit. Once it posts to your wall you will be able to go into the group chat on the destiny app.