If you have an account on Meta Stack Exchange, you have an account on its meta site.
You do not need to create a separate account for meta; once you are logged in on Meta Stack Exchange, you are also logged in and may post on its meta site.
Votes on meta do not affect your reputation; your meta reputation is the same as your reputation on Meta Stack Exchange (synchronized hourly), though you earn separate badges. You must have 5 reputation to participate on meta.
Meta SE doesn't have a meta site!