This cannot be done manually.
At start-up, the unit checks for a DHCP server. If there is one, it takes the DHCP address provided by that server. If there is no server, it starts using a link local address after a couple of minutes.
Note that if you switched the unit on before connecting it to the DHCP network it will not switch to DHCP. The physical connection to the DHCP network needs to be made before powering up the unit. If that physical connection was not there first the unit needs to be restarted.
On PC, it should also be noted that the MADI X8 will not be detected if the Bonjour service is turned off (Start button > Setttings > Contol Panel > Administrative Tools > Services).