To mass / bulk send objects to a call list in Salesbox follow this flow

1. Go to the preferred section

2. Open the advanced search and either search to limit the list or not

3. Click the edit icon in the bottom right corner of advanced search and select mark all

4. Click the phone icon

5. Select what call list to send the contacts or Accounts to 

6. Click done

All objects that was selected will now gets added to the selected call list.