Depending on what you're trying to do, there's two ways of doing this. If you want to be linked to instructables, but don't want them posting on your wall. The next time they post, click the x button, and a pop-up will come up and ask if you want to not allow instructables to post to your wall ever. Just say to never allow.If you want to not have instructables linked at all, you can click account - account settings in the top right corner. Then click Applications on the left side menu. You should see all the applications that are linked to your account, "x" whatever you want to get rid of.