You should have ordered a replacement SIM and not a new SIM.
Then you follow the activation process here so that the SIM is linked to your existing account/membership/number etc.
If you got a brand new SIM rather than a replacement SIM then contact 48 support and get advice from them on activating it as a replacement so that it's linked to your existing account/membership/number etc.
If you activate a new SIM as normal then it will be a new account/number etc. and you don't want that presumably.
Hope this helps.