If you purchased a miniDSP platform with Dirac Live license (E.g. SHD/Flex with Dirac Live/DDRC series), you do NOT need to activate anything. The Dirac Live license is already flashed inside your unit. Just follow the manual steps and you'll be al set.
If you purchased a unit without a license (E.g 2x4HD/Flex/CDSP 8x12), then it's a different process as you will first need to "purchase" an upgrade from here. https://www.minidsp.com/products/dirac-series/dirac-live-upgrades and follow the steps described in each product page.