If you're in configuring the MX as a warm spare in High Availability, you only need to ensure it has an IP address (manual config or DHCP) and once connected, it will sync the rest of the config from the cloud.
If you're in configuring the MX as a warm spare in High Availability, you only need to ensure it has an IP address (manual config or DHCP) and once connected, it will sync the rest of the config from the cloud.