Whilst this is relatively self explanatory there are a few things around doing this that are useful to know
Log into the SDX and go to Configuration > Management Service > Backup Files > Action > Factory Reset
You will be presented with the following three options
Reset (Without Network Configuration)—Retain the IP addresses of the Management Service and XenServer. This option destroys all VPX’s also wipes the licence file, certificates but keeps the current active firmware of SDX. It also keeps the SDX network configurations like LACP bondings
Reset (With Network Configuration)—Management Service and XenServer restart with the default IP addresses (192.168.100.1 for the SDX Management and 192.168.100.2 for Xenserver) This option destroys all VPX’s also wipes the licence file, certificates but keeps the current active firmware of SDX.
Appliance Reset—Completely wipe out the device. Loose everything configured (network, certs, vpx’s, licenses etc) but also the appliance reverts its firmware to what it was delivered with.