Ok lew
To start with.....welcome....you los focer!!!
Secondly-hit reply to add on a normal reply on this topic as you've already done to ask the question.
Add text to text box as per normal
Below the white text box is a +additional options
Click the +
Click "choose file", upload a file
Click post
Simples!
Theres another way,but i havent figured it out yet as pics always go into the forum folder but hey at least this will get you started.
Looking forward to seeing the beast!