Assuming you are referring to an LTE SIM card for a mobile device:
To activate your SIM provisioned, you will need to contact your carrier. Each carrier has their own process for activating LTE SIM cards. In general, you will need to provide them with the SIM card number (ICCID) and some information about yourself and the device you are using. Once they have verified your information, they will be able to activate the SIM card and provision it for use on their network.