The first and foremost thing, is you need to have social media accounts such as:

Tumblr
Instagram
Wattpad
Twitter
Snapchat

Those are all optional obviously, but you DEFINITELY need Tumblr.

Next you need a unique username. Most websites, you can't put the app name into your username. Try basing your username off of hobbies of yours. Or your 'style/theme'. 
My username doesn't have anything to do with either of those, it's just my name, but it's still something that relates to me.

When it comes to being a Tumblr girl, you need to have a style, or "theme" that you go by.
Some of the "themes"/styles are:

Girly
Grunge
Hipster
Indie/pop
Boho
Nerd/Geek
Swag

Once you pick your style, or the style you want to start being apart of, you need to express it in yourself and social media. For example, you could have a certain Instagram or Tumblr theme. My instagram theme, is a certain filter that I 'created' using multiple settings on VSCO. I have one row of faces, the next row is bright white Tumblr photos. Then another row of faces, and so on and so on.



Others may have an account with pastel colours, or dark colours. Maybe even mint green.
My point is, find your own way to express yourself, so people know who you are.

Another good way to express your 'theme/style' is by what you wear and how you look.

The next chapter will get into that.