error to configure distribution in replication in sql server 2008

Simple answer: You do not have permission to do what you are trying to do, hence the error message saying "Access denied." - You will probably need to use a login with greater control over your database i.e. more permissions, i.e. an administrator (or if you are admin, super administrator and if you don't have something higher than admin, give yourself the required permissions. If you can't do that, contact your SysAdmin, if you are SysAdmin, good luck to you because I can suggest nothing further other than to give yourself the necessary permissions.)

Hope this helps,
Ed