You can visit your user's settings page by navigating through the web interface (under your avatar's drop-down list) or visit https://github.com/settings/profile directly:
For example, here is how my settings landing page looks like:
We are going to analyze the most important settings GitHub provides.
Under Personal settings, you can see the various options that you can customize to your liking.
The Profile settings is where you can fill in your personal information so that people know who you are. Consider it like socialization. After all, GitHub is the Facebook of geeks.
All the profile information is optional to fill in. You can see how this will look by visiting your username page at https://github.com/<username>.