If you've defined two targets in CMakeLists.txt they both will be generated and Qt Creator will auto-detect and add them in the project tree (as well all the subprojects you may be adding via add_subdirectory).

As for building and running you need to select desired target if there is more than one to choose from. You can also modify active targets list in Project view - open details of cmake build step (by default there is only single build step).

The reason that a part of project is grayed-out usually means that cmake encountered an error and did not finish configuration. Please notice that this situation will be explained in message logs (bottom area in Qt Creator). Quite likely you have some errors in CMakeLists.txt that need fixing or something else is missing in project setup.