Step 1 : Go to Facebook Events Manager, make sure you log in and choose your business account

Step 2 : Choose the Pixel ID you want to set up conversion API

Step 3 : Go to Settings, scroll down and click Generate access token under Conversions API section

Step 4 : Copy the token appearing, make sure you save it somewhere else as Facebook won't store it.

Step 5 : Paste the token access into our app