To clarify what the instructions are trying to say/do (trying to keep it simple)
Change the LAN address of your router to 192.168.0.100 with Subnetwork Mask 255.255.255.0 (Or Subnet Prefix Length 24).
This will change the address that you need to use to access your router after the change has been made so make a record of this change for future reference.
You must use this address to make any changes to the router in the future or to monitor you Internet connection.
After making the change you will need to restart ALL equipment connected to your LAN (whether they use Ethernet and Wifi) so that any device that uses DHCP can pick up the changes that have been made. This will include the device that you connect USB connection to if it also uses the WiFi or Ethernet.
Note however that if you have any devices that have statically defined (Manually set) network addresses that you will need to reconfigure these manually (IP address between 102.168.0.1 to 192.168.0.254 but not 192.168.0.100 or 192.168.0.111, subnet mask 255.255.255.0, default gateway 192.168.0.100, DNS probably needs to be set to 192.168.0.100 or your ISP provided value.
Changing the LAN address on the router may cause issues with the DHCP service which assigns addresses to devices which connect to the LAN/Wifi so you may need to review the DHCP settings on the router, 192.168.0.100 and/or 192.168.0.111 may be in the DHCP scope and this may cause address conflicts.