Modifiying selection screen of report RIQMEL20 coming from LDB 'QMI'

It is intended to modify the SAP standard report RIQMEL20 . This report RIQMEL20 is using the Logical Data Base "QMI" for the selection screen block & data selections which we need to modify. That means we need to modify this SAP Standard LDB "QMI" to add these extra fields & logic.

When we are try to change this LDB it is asking for a access key. Also we don't know the implications of changing this standard LDB.

How we can add the extra fields & its logic?