1. Go to http://console.developers.google.com 

Sign Up if you don't already have an account.

2. Create a new project or use an existing one.

3. Enable YouTube Data API v3 by clicking on "Enable API's and Services" and search for "YouTube".

4. Click on Create Credentials > API Key

5. (If you are asked) Where will you be calling the API from - select "Web browser (JavaScript)" from the drop down.

6. (If you are asked) What data will you be accessing, select "public data". 

7. Click on "What credentials do I need?" button.

8. Copy/Paste your API key to Content Gorilla and click authorize.

You're now ready to start using Content Gorilla.