^^ You can go to the FAQ via the link above for detailed instructions, but the remaining checklist of requirements for simultaneous voice/data if you've already installed the update is:
Enable "HD Voice" feature on your line via My Verizon app/VZW website/calling VZW, wait a few minutes and reboot, double-check that "Advanced Calling" is 'on' under settings, and make sure that you're in a location with a 4g signal.