The meta-cartridge looks for geo:long and geo:lat items in the source graph being enriched then searches against Foursquare to get nearest foursquare venues. The URL is then exposed as an foaf:based_near link in the source graph. When de-referenced, this link is materialized by the Foursquare cartridge into a Linked Data representation of that venue's Foursquare profile.
The Foursquare meta-cartridge must be configured with a Foursquare Oauth token. These are specified through the cartridge options oauth_token. It can share the same Foursquare API and Oauth token used by the Foursquare extractor cartridge. For details of how to configure the latter, please see here.