How do i pk in runescape?

alright im getting a little tired of my friends having so much money and saying its from pking. i wanna pk so badly but i just suck at it i always die and lose alot of money can anyone tell me how to pk with 79 att 83 str and 74 def im a level 99 but says im 108 because my summon level is 66 so can anyone teach me how to pk with my stats and i forgot to say im a p2p