If there are no parameters to pass, you can simply call the function without the parentheses.
To pass actual values, you can use commas as placeholders for parameters.
SQL> SQL> CREATE OR REPLACE FUNCTION squareme(thenum number) 2 RETURN NUMBER IS 3 BEGIN 4 RETURN thenum * thenum; 5 END squareme; 6 / Function created. SQL> SQL> BEGIN 2 DBMS_OUTPUT.PUT_LINE('9 squared is ' || squareme(9) ); 3 END; 4 / 9 squared is 81 PL/SQL procedure successfully completed. SQL>