So you either have the 'free' lvl 60 token or you buy the 60 token off the gtn/cartel and use the token like you would any other unlock. Once you use the token (or have the free one)you can go back to character select screen and a new option under create a character will appear to let you freely boost a lvl 60 character. As far as I know once you use the token it's unlocked account wide and it can only be refunded (after successfully creating a lvl 60 character) by deleting that same character before you reach lvl 61. If you play the character long enough, you will unlock it's buffs, and whatnot, seemingly automatically. Good luck.