1- Go to https://apps.twitter.com, sign in your Twitter account and click on the “Create new app” button
2- Fill the name, description and website with what you want and the “Callback URL” field with https://script.google.com/macros/ (very important, else TAAS will not work!). After that, go to the bottom of the page, agree with the Twitter terms and click on the “Create your Twitter application” button.
3- Congratulations your app is created ! Now click on the “Keys and Access Tokens” tab.
4- Here you can find your Consumer Key and Consumer Secret. You just have to copy/past them in your TAAS account and you are all set!
Then go to this page and follow the instructions to add your phone number to your Twitter account.