The Activity Management module is not included in the default Dialog Insight packages. You must have it as an additional option to access it. Access is given at the company and project level.
If you would like to make it available to your team, you must request it in order to receive the multiple benefits of managing activities in Dialog Insight.
Contact your Dialog Insight account executive or go through support and they will take care of the request. All activation details and fees will be provided to you.