Im a 12 year old Girl and I wan't to make a website but I don't know what to do with it

Livy Loola,

Just 12! You can go to blogspot.com and create your blog...

Do not think of making your website, yet, as you are a kid, and making website needs you to spend some money. Not some, but much. Can you?

I think you can for the time being use blogspot for the passion, purpose and profession, if any.

Hosting is available for around $6 a mouth on a two year contract from several vendors this is shared hosting with unlimited bandwidth and storage. Because you share a server with other sites heavy traffic can cause problems.
If you want to just publish content Blogger or Word Press offer free sites. If you want to learn the workings of a site you should get a hosting package and install a script like Drupal or Joomla

First at 12 you get your parents permission to even have one first. Since it can be dangerous for young children to have too much personal data online.

Next there are dozens and dozens of free sites that you can create a web site for free.

What you put on it, is up to you and your parents.