CaesiumCLT is based on libcaesium and requires it to be compiled.
Please refer to its own documentation.
You will also need cmake if you want to compile it from source.
For Windows you just need to download the latest release package from here.
Unzip the package using your favorite software, open it and run caesiumclt.exe from the Command Prompt or PowerShell.
NOTE: Homebrew installation will come soon. Use Linux instructions below for now.
Download the latest release package from here or clone from git.
Then run:
$ cd caesium-clt
$ mkdir build && cd build
$ cmake ..
$ make
$ sudo make install
This will compile and install caesiumclt in your PATH.
You can verify everything went ok by running caesiumclt -v.