Syncs
Manually adding every Series would be tedious for any library of meaningful size. This is where the idea of a "Sync" comes in.
Syncing allows Series to be automatically added to TCM. You can Sync from any non-TMDb/TVDb Connection; each Sync can be customized to only add filtered subsets of your Series, and can also automatically assign specific Card customizations through Templates.

For most users, I recommend Syncing from your primary Media Server (Emby, Jellyfin, or Plex). You can use the sidebar to navigate to the instructions which suit your set up.
The tutorial uses Breaking Bad as the example Series. If you do not have it in your library, add it temporarily or pick a different Series and apply the same steps.