Log into www.google.com/adsense.
Click on the "sign up" button. A form will be displayed as below.
Fill the form and click on "submit form" button.
When you fill the form then you will be shown your information overview.
If the given information by you is true then go down.
Then they are asking that "what describes best you". There is two option.
1. I already use google services. I have a email and password
2. I don't use google services then create you own site.
Just because we have created an email account above then select the first option that you have already an email and password.
Then they ask you that " Do you want the existing user name and password to be your google adsense user name and password"
Just click this option that yes.
Then write your gmail user name and password and then click "sign in" button.
You will be notified that your google adsense account may approve in 1 or 2 business days.