This config option defines the addresses for the device being configured. It goes under the [Interface] config block and it varies depending on what the wireguard node is doing. If this node is acting as a router for other clients on the network (bounce node/router) It should be a subnet assigned to the interface, similar to how you would assign a subnet to a routers interface. IG; 192.0.2.1/24 or 2001:DB8::/64
Specifying multiple addresses should be done with comma separated values of each subnet/address using CIDR notation always.
IE; Address = 192.0.2.1/24,2001:DB8::/64