The first thing you need to do is apply for a developer account. You can do this here . You'll be ask to subscribe for $100/month but under you can see "Subscribe" for free. Next describe what your app is about and once you are done with that you will be taken to the developer page
In the developer portal, you'll either automatically create a project and an app when signing up for a new free account or manually if you already have an account. Ensure your environment is set to production for tweeting. You'll receive an API Key, API Key Secret. Save these.
Navigate to “User authentication” and click “Set up,” which takes you to a page with several input fields:
Navigate to the “Keys and Tokens” tab at the top of your app's page and go down to the “Authentication Tokens” section. Click “Generate” next to “Access Token and Secret” to receive your access token and secret. (You might also see the API Key, API Key Secret, and Bearer token displayed again if this is your first time generating an access token.)
Ensure on your “Keys and Tokens” page that the access token has been set up with both read and write permissions.
Thats it you have all 4 API keys to start using the extension.