Hello,
You can use the $ifconfig command to configure the network just as it is shown in the following image.

If you want to do it in the code, you can do it by using the bind address function:
IP_IF_BindAddr6(ifHandle->ifUniqueId, &inIpAddr,ip6AddrTypeManual_c,
IP6_ADDRESS_LIFETIME_INFINITE, 64U);
Best Regards,
Estephania