How to change APN settings if not shown on my iPhone 6S? I am trying to connect to Verizon

I purchased an iPhone 6S in April 2016 in Germany, and used it on a network there. I have moved to the US and am attempting to use the same phone on the Verizon LTE network with Verizon's SIM card. But, it will not connect to a network, and I cannot see anywhere in the iPhone Settings any options to modify the APN.