Okie, if I'm understanding you correctly, you want to attach a document to a post?

If that's the case, you can reply, or make a post... one of the automatically "checked" boxes is "I want to preview my post and/or attach a file". Click "Continue" and just above the "Ok, submit" button is a line that says "You may attach a file if you like (no bigger than 300000 bytes please)." (and includes a box with a "Browse..." button. )Click the button. Locate the file you want to attach, click "Open" and then click "Ok, submit" and voila, a document is attached!

As for doing things in Chat... pressing "CTRL+V" should open a dialog box in Chat where you can post things.