When you initially try to install the FLG integration, you will see this popup:
To find or create your API key, access FLG as you normally would. You will probably need to log in. Go to Settings (1), Configuration (2), Access Keys (3).
If you already have an Access Key, you can use it, otherwise you'll need to create a new one (4).
The Key must have the following access: (you might need to Edit an existing key to include these)
The Domain is a unique identifier for your account, which you chose or were allocated when setting up FLG. Look for the URL in the top-left corner of your browser window - it should look like this:
In the above example, the part we need would be yourdomain - you'll need to copy this and paste it into the popup on our integrations page before clicking Install.