Step 1:
Go to settings > Connections then tap on SIM card manager
Step 2:
Select Add mobile plan then navigate to Other ways to add plans
Step 3:
Choose Add using QR code then scan the QR code
Step 4:
Follow on-screen prompts
Step 1:
Go to Settings > Cellular then select Add cellular plan
Step 2:
Choose Add using QR code then scan the QR code
Step 3:
Follow on-screen prompts