The discord link is now fixed !
To digitalize a digimon, you need to learn the core ( so in your case, that step is done )
After that, you need to go the Digitalizion tab, and search for the core you learned.
To help you, there is a number on the core learned, you just need to find the corresponding page in the Digitalization tab
If you need more help, I can show some screenshots on the discord, so feel free to join it !