Hi,
It depends.
I'm not sure that HikaSerial and the point generator will be the specific solution you need if you want to give points to user after a purchase.
HikaSerial with the point generator will give a serial to the user and this serial can be "consume" in the front-end in order to give some points to the user ; the idea behind that is to let the customer give the "serial" to someone else.
If you just want the user to earn points after a purchase, the HikaShop plugin "user points" will be more appropriate.
Otherwise, in the tutorial, in the section "Creating the first pack" it is specified :
In the configuration of the pack, you will be able to choose the generator previously configured.
which means that you have to select the generator you configured for the option "pack generator".
Regards,