First, go to Integrations. You can do this by clicking here.
Next, retrieve an API key from Lucca. You can find it here:
Click Generate a New API Key.
You will now need to enter your API details. They should look like this:
You will now see an API key displayed in the red field. Copy this API key and paste it into Salary.
Next, in Salary, open the integration and go to External Fields. From there, you can map the data between Lucca and Salary.