how to overcome resistance to use the CRM

We are implementing the CRM, sugar crm for our sales and marketing activites, we have rolled out the CRM but still users are not yet started, Iam from IT (IT HEAD). I want to take up this to upper management can anybody give me the suggestions how to make users start working with CRM, what all the measures to be taken to overcome the resistance of the users for not starting to use the CRM.

Please provide the best practices tips or instructions to be taken from the management to overcome the resistance for using the CRM.