I need information on publishing!?

I'm currently writing a story about a girl who is writing a story (haha it's confusing). She's a teenage writer (just like me) and she decides she wants to get her story published. Could anyone tell me the process on publishing or self-publishing? The publishing in my story needs to be done very quickly so would self-publishing be quicker? Please give me all information you know about publishing and self-publishing (costs, where to go, how long it will take for it to be fully published and available to buy, etc)! Thank you in advance :]