Noisy Lifters

[ClassicAU]

I have already done a search on this, and it returned some good unformation. Apparently in order to stop the 'tapping' noise coming from my engine, i need to use some Nulon Lifter Free solution.
What I didn't seem to find though, was where abouts do I use this? I know its a dumb question, but I just want to be sure. I assume I just put it in where the new oil goes through the Rocker Cover? I am fine to just add this as is, or does the oil need to be changed?
My guess is that this has started happening because I thrash the c**p out of it most of the time I drive it. Which is usually only on the weekends now, and on the odd day after work. So this solution will be ok for now, or have I gone and killed my poor motor?

Evan