To access the Audit-view, you will need to add a virtual role named "AuditAdmins" as adding virtual roles makes it possible to make the assignment of roles more flexible:

<episerver.framework>
<virtualRoles addClaims="true">
  <providers>
    ...
    <add name="AuditAdmins" roles="CmsAdmins" mode="Any" type="EPiServer.Security.MappedRole, EPiServer" />
  </providers>
</virtualRoles>

</episerver.framework>

And then create a group in the CMS called AuditAdmins and assign the relevant CMS users to the group. If you're already logged in, try logging back out and in to see the tab.