Hello @BERNIEGX20
You won't find a setup solution for what you plan to do.
Your FIOS Router already has a private IP-range (RFC 1918). By default the range should be 192.168.1.0/24. The router has the default-IP 192.168.1.1.
You connect the GX20 to the IP-range of the FIOS Router, so the WAN-Port (Port1 on the GX20) get's an IP 192.168.1.x. x stands for the number assigned by the FIOS Router to the GX20. If you log on to the GX20 it will allow you to create VLAN's. Meraki Go - Wired Networks (VLAN) - Cisco Meraki The VLAN created on the GX20 has to be different from the one on the FIOS Router.
The VLAN you create on the GX20 won't be accessible from 192.168.1.0/24 due to firewall-settings on the GX20. Unless you set some port forwarding rules on the GX20. But that's a different story. The GX20 alone doesn't allow wireless connections. If you want to have wireless access to the VLAN created on the GX20 you'll need additional hardware.
This may sound odd: Why don't you create a wireless guest network on the FIOS Router for the people you want to give internet-access but no access to the LAN? In this case guests will have to use the wireless guest network and won't be allowed to have a wired connection. Only people allowed to the wired and non-guest-wireless will have access to your server.
hope it helps