OS? Compiler?
This looks to cover it in great detail for windows / visual studio 2019
https://support.dcmtk.org/redmine/projects/dcmtk/wiki/howto_cmakeconfiguration
to boil that down, these 2 paragraphs seem relevant:
Introduction
Note that CMake itself does not compile the DCMTK, but is used to generate project files (e.g. Visual Studio under Windows, Makefiles under Unix, XCode under Mac OS X) that can then be utilized for starting the compile process.
The fast way
If you are not interested in any details and just want to build DCMTK with all the standard options, you can hit the Configure again, and, if it runs successful, hit Generate. Then you have a project file in the build directory that you have chosen at the beginning and therefore, your task with CMake is completed here.
so if you just download it and fire up cmake it should give you a project file for visual studio that will then compile the whole thing into library files you can use.
I would get it working like that, with just the defaults, and see if you can build a simple example program using the library and kick the tires on everything. You can play with rebuilding it for performance or specific needs later.
if you have never used a library before, this may be a bad place to start -- this thing is massive and complex. You may want to do something simple first to get a feel for the process. Like, zlib (make a simple zip file) or something.