For WireGuard in general, you provide it an AllowedIPs config which is a list of CIDR ranges that should be routed across the link. That could be `0.0.0.0/0` (aka everything), a single subnet, a union of several, or even individual IPs. This config is technically symmetric between the endpoints, though a prototypical implementation of "individual clients enable the VPN to access the internal network" may limit the "client" AllowedIPs to an individual address.