U cant.the raptor mount is the first mount u get from the PoF story.you gona get into the story and kill some story mob.i would suggest you to clear some tyria map completion and get 80lv.once u get it then u get a full zerker set exotic gear.its kinda easy. you can buy from TP/ wvw token and some reward from achievement.once u get it then u switch ur story to PoF. the story start on Lion arch. then u will get into crystal desert.