Understand security roles
Give members of your team different levels of access by setting up security roles in Microsoft Dynamics CRM. Each security role provides a set of privileges that define whether users can read, write, create, delete, or share records. You can set whether these privileges apply to a user, a business unit, a business unit hierarchy, or the entire organization. The following links tell you more about the different types of security in CRM and how to assign security roles to users.
TechNet: Security concepts for CRM
TechNet: Assign a security role to a user