QuickBooks should be open prior to importing Clients. This is not required but speed will be improved.
You can click the check box next to multiple Clients to import them into SIX.
There are column filters:
There are filters in the ribbon for showing All, New, or Matched Clients. The New filter shows only Clients who don't already exist in SIX. The Matched filter will shows only Clients that already exist in SIX, use this for updating information for existing Clients.
There's a search field:
Once finished filtering, you can use the [Select All]/[Deselect All] buttons: