Why are the pads longer than the corresponding part of the panties?

Your panties stretch with you. The reusable pads do not stretch. Therefore, the pads are slightly longer than the corresponding part of the natana panties. However, the pads should fit smoothly when you wear the panties.

How do I attach the pads to the panties correctly?

You simply attach the pads to the panties with velcro. You do not have to attach the hook and loop fastener so that it lies 100% on top of each other. This gives you the opportunity to position the pads optimally for you.
You can adjust them with the velcro a little "tighter or a little wider".

If the pad "ripples" when you wear it, it is too loose and you should fit it so that you use the inner ends of the velcro. If your pad is too tight and the bottom of the panty is sagging or the pad is coming loose from the velcro, please use the outer part of the velcro on the pad in order for your insert to have more wiggle room and - when you pull up the panty - fits perfectly.

For most sizes, the shape of the pads and the length of the velcro fastener immediately show in which direction the insert is attached to the brief. However, if you wear a size where the shape is almost symmetrical, you can still orient yourself by the velcro closure. With the strong inserts, the position of the reinforcement provides additional guidance. It sits further forward in the pad.