You need to do this yourself.
Assuming that your phone is unlocked for use on any network then once you activate your SIM and insert it into the phone then you should be able to receive calls and texts and use mobile data.
If you buy a membership plan then you should also be able to make calls and send texts.
What exactly is or isn't working for you?
If you need to contact 48 support about this then see the links in my signature below.
