"Topping off", or "topping", or "pruning" is the practice of simply cutting a plant down a bit from the top. In other words, reducing it's height. You don't need a tutorial - just take your pruning sheers and whop off a section. Why would one do this? Chile plants only produce pods at the nodes - the places where stems branch off from each other - and topping off makes the plant create more stems. More stems, more nodes, more pods. I don't do it, as I usually have more than enough pods for my needs.
I topped my anuums when thye started to grow into the lights before I could raise them... (the chinenses were still too short)... they recovered just fine--turning into 2-3 plants instead of 1. One of my dogs "pruned" a serrano for me the other night... lol