You can access the Google AdWords home page at the following web address: http://www.google.com/adwords.
You will need a Google username for using the Google AdWords. If you have a Gmail account then you can use your Gmail username, or if you choose to create a new Google username for the AdWords service, then you may do so by clicking on the Start now button shown in the following screen shot:
You will be taken to the Create Google Account page, where you can choose the user name and password you'd like to use with AdWords.
In this step, you need to define your time zone (from where you operate Google AdWords account) and the currency in which you will pay for your ads.
Note: Time zone and currency settings can't be changed after you setup your account.
During step 1, if you decided to use the existing Google account (e.g. your Gmail account) to create an AdWords account then you do not need to follow this step. However, if you created a new Google account for AdWords then you will be required to verify your account.
After verifying your account with Google you will be able to sign in using your username and password.
You can use your AdWords account (e.g. create campaigns, create Ads, etc) without activating your account. However, your ads won't run until after you provide billing details, which is a required step for activating your account.
In order to activate your account, follow these steps:
Note: There are one time account activation fees. Account activation fees and payment options vary according to the currency you use and the location of your billing address.