After you CRM 2015 upgrade, the users, teams, and roles should now appear in the Settings area under “Security Management.”
However, what should you do if the new security management section is missing?
Create a solution containing your sitemap and export it out.
Edit the sitemap and add the following subarea to the settings area:
<SubArea Id="nav_security" ResourceId="AdminSecurity_SubArea_Title" DescriptionResourceId="AdminSecurity_SubArea_Description" Icon="/_imgs/area/Security_32.png" Url="/tools/AdminSecurity/adminsecurity_area.aspx" AvailableOffline="false" IntroducedVersion="188.8.131.52">
Import the solution back into your CRM environment, and after a refresh, you will now see the Security Management section.