Each time you add a constraint, it is implicitly using AND:
[query whereKey:@"username" equalTo:@"admin"];
[query whereKey:@"location" equalTo:@"USA"];
translates to "username == 'admin' AND location == 'USA'"
UPDATE
Your specific case as an example:
PFQuery *beneCodeQuery = [PFQuery queryWithClassName:@"RemittanceTable"];
[beneCodeQuery whereKey:@"beneCode" containsString:_beneCodeText.text];
[beneCodeQuery whereKey:@"remittanceAmount" equalTo:amount];
NSArray *result = [beneCodeQuery findObjects];