How to insert the record in Internal Table

Hi Guys

I am creating one report . In which i want add record in Internal table from another internal table.

but in my internal table there are only few records but in table in which i want add the records there r more records is it possible to add more records in internal table.

eg

in itab_final there 5 records & i want add records i_source there are 10 records how to fill up data.