The old J pipe basically disintegrated in my hand when I pressed my thumb against the leak. So I bought a new one, matching it exactly to the metal one I removed. I asked them at Lowe's about joint compound and they said use plumber's putty. Here is my question: How does one use plumber's putty? This may sound silly but I have never done any plumbing repairs and while the J pipe fits snugly, I don't want it to leak again. Please instruct me and thank you for your time.