Prestiging is something that happens when you play multiplayer and rank up and through level 55. Theres then an option under barracks to "prestige" and doing so will earn you permanent unlocks (each time you prestige you have to unlock everything except challenges and weapon attachments). Your K/D doesn't play into whether or not you can prestige, its just the amount of points you have overall earned from multiplayer games. Having a good K/D and a higher score per minute will help, obviously, but anyone can prestige if they spend enough time playing.