To use Twitter counter widget and other Twitter related widgets, you need OAuth access keys. To get Twitter Access keys, you need to create Twitter Application which is mandatory to access Twitter.
Go to https://dev.twitter.com/apps/new and log in, if necessary. You will get a page as following
Enter your Application Name, Description and your website address. You can leave the callback URL empty.
Accept the TOS, and solve the CAPTCHA if necessary. Submit the form by clicking the Create your Twitter Application
Now click on “API Keys”. You will get a new page as following.
Now click on “Create my access token” and you will get a new page as following.
Keep your API key, API secret, Access token, Access token secret at a save place to use on your website later.