If it's for federal party, the donation amount is entered at field 409 on page 2 of schedule 1;
if it's for provincial party, enter it into a similar field on provincial tax (e.g. field 6003 of form AB 428) or credit form (e.g. field 6310 of form ON 479), depending on which tax province you live in.
AB Tax form, AB 428
ON Credit form, ON 479