How to attach License file to dowloadable products.

The 1.5 feature list shows:
• Downloadable Products  ◦License file can be attached

I have just upgraded to 1.5 but I can't seem to find the above option.
Am I overlooking something ?

Lex

Go to an order details page (back end), then 'Products' tab. Upload a license file for a downloadable product.

Thanks, I found it.
Unfortunately it's not the feature I am looking for. I am looking for a way to automatically generate a license code and then either attach it to the download or stick it in the customers e-mail. The license code could come from a uploaded list or from a keycode generator.
Guess I have to implement it myself.

Lex