Name & Username: The name which you have given while creating the facebook page will appear here in the name section. You can create your own username of your own, you can click on the username and create your own username. Try to use your business name or brand so that people can find you easily. You will get an URL of facebook according to your username, so be sure of selecting the apt username. Even you can edit it anytime but there should be an availability of the username at that time.
Invite Friends: If you already have an account and the page is correlated to your account then you will get a pop up below as shown. You can Invite Friends to like your page and follow the page.
Add Button: If you click on the add button, You will get a pop up as shown in the below image. This is one of the call to action button which can help you for the conversions.
Add Description: Write down the short description or the summary of your business/brand. What is your business is all about. Have everything intact ready before you start doing marketing for your facebook page. Even you can add an image there.