LAN behind Broadband Router/Modem - NAS setup

. I have set up 3 CPU’s (laptops) as fixed IP (static) through internal LAN cards IPV4, connected the printer (share) and HD to LAN Wireless router Synology) Following this I have tried to set up a static address for the EX4100 NAS. However, now it does not work. Can I have a static address and if not how do I go back? Thank you