Well, first, you need to make sure you have patched Concealed the Conclusion to v2.01. But, all you have to do is just pase the "th_dnh" folder from the SCC to where the th_dnh folder that contains CtC is.
And yes, it's essentially a much better Spell Practice mode, and all cards are unlocked (although any work done there will not add to the stats in CtC). It also includes a second set of Last Words, although most of them are just a harder version of an existing Lunatic spell card that character has.