What? No girls? YOu had it easy!
Sorry HC.
In regular JU (not the forums), on the left you will find a line that says "My Articles". Click it and it will bring up your articles, with the most recent being first. At the bottom of the article, you will see the word edit. Click on it. Then the article will appear just like when you first created it. On the left, you will find the box that says "Select who can respond". Change it to no one. Then scroll down until you see the submit button (as before) and click it. That will disable commenting.