You don't INSERT
into PL/SQL collections like this.
You could do a BULK COLLECT
from the table into your collection but then you could only be selecting one column from the table. Assuming your intention is to select the key and the value, you can do something like (assuming I've guessed which column is the character key and which is the numeric value)
FOR i IN (SELECT ID_WNIOSEK_ORG, ID_WNIOSEK FROM ZC_WNIOSKI)
LOOP
WNIOSKI_MAP( i.ID_WNIOSEK_ORG ) := ID_WNIOSEK;
END LOOP;