how to asign a value set security rule to a role?

Hello,

I created a value set for Receivables application and then I created a value security rule for that value set. My idea is to create a flexfield with that value set for the Manage Customers task, and then, grant access to users by creating a custom role with that security rule i created. I need to know how to a sign the securiry rule to the role. I will attach the steps made

Thanks for the help!

Gabriel.