Here, you can select which forums included in the import package will be imported. Unless you are importing to an existing site, the following option is available:
• | Import all user memberships - if checked, user memberships will be imported together with the selected groups. |
Detailed information about the built-in export/import functionality in Kentico CMS can be found in Developer's Guide -> Managing sites -> Export and import.
Page url: http://devnet.kentico.com/docs/6_0/contexthelp/index.html?importgrid_community_group.htm