Add a user Navigate to Jenkins -> Manage Jenkins -> Configure Global Security.
Under Authorization you need to configure who can do what. You can add LDAP groups and/or users and fine tune what they are allowed to do.
If you enabled Matrix-based or Project/Matrix-based authorization then you have a field to add new users/groups. You can add users that are known to LDAP or not known.
Add Credentials
If you added a user that is not known to LDAP you need to create the credentials in Jenkins (i.e. password).
Navigate to Jenkins -> Credentials -> System -> Global Credentials -> Add Credentials
Then add username and password.