The only way I could do this was by populating the table jos_comprofiler_fieldvalues from phpMyAdmin, importing a CSV file I created from Excel, with the same fields this table has, taking into account the same fieldid. It's not the best way but it worked.
It would be great if you could do this directly from the GUI of Community Builder in the backend of Joomla.
Meanwhile I hope this helps other people with the same problem.