Below the Facebook Access Token field on the settings page, we have a link to this article for information on how to retrieve it: https://smashballoon.com/custom-facebook-feed/access-token/
You only need an access token if:
1. You’re using the “Native” count option, AND
2. You’ve tried it without a facebook access token and are getting no FB counts
In most instances you can retrieve FB counts without an access token. While undocumented, I believe Facebook limits the “no access token” API usage by server IP, so if you’re on a shared host with lots of people querying Facebook you may have issues and need an access token.
I highly recommend you don’t use the native counts, and instead sign up for a free account at SharedCount.com. You don’t have to mess around with Facebook access tokens, and if you are retrieving counts from multiple services this will keep the actual API queries to a minimum (SharedCount.com will aggregate many services into a single API query).