network: use Time Capsule as a shared disk via Ethernet

I have tried to configure my Time Capsule as a disk via Ethernet for two days, following several instructions on the Internet, most of which seem to be too old. I get lost in the WAN / LAN configurations and in the different configurations of DHCP / NAT routers (I'm NOT a network type, I'm just a type of software that omitted the networks). Is it possible to have a Time Capsule as a disk via Ethernet while you have a separate router for the Internet? If so, could someone share images of your configuration, both on the TC side and for the Network configuration on the Mac side?