There is only one setting related to the Friends module - Friends management path. It is located in Site Manager -> Settings -> Community.
Its value determines the node alias path of the page on that the Friendship management web part is placed. This is a special web part that handles friendship management actions from friendship request e-mails.
If some user receives an e-mail with friendship request, there are links for friendship approval or rejection included in the mail. When the user clicks one of the links, they are redirected to this page and the user guid and type of action is transferred in form of querystring parameters. The Friendship management web part processes the received parameters and performs the necessary tasks for friendship approval or rejection.
Page url: http://devnet.kentico.com/docs/devguide/index.html?friends_settings.htm