That's what I did, remove the SiM card from my LG G7, insert in the 4XL and in seconds I had 4G Verizon service. I'm on a MVNO provider US Mobile that uses Verizon towers.
You can use your already activated SIM from your old phone and use it on the 4 XL. Only if you need a new SIM you might have to drop by the store but even that you can do online and they'll deliver to your house. Generally I just use my old SIM from the phone I'm replacing.