There are a few different ways that you can get Google Test and then set it up to begin using it. The Google Test documentation skims a bit over the basic starting steps, then presents perhaps a choice overload for a lot of later steps. I have no doubt it’s the best overall reference available, but it’s not necessarily the best guide for someone who just wants to get started. You might find Google Test integrated into some of your tools (for example Visual Studio 17) – so that may be easier to use than this guide, depending on your needs. The method in this guide gives you flexibility and control over how you use Google Test.
Since my own interest was in setting up Google Test on Windows, this guide adds Windows specific details in parentheses. This may help clarify some steps regardless of OS. But aside from the parenthetical information, the steps should (hopefully) work for any OS.

Quick Steps:

1. Get the git repository for googletest.
   1. Open a command prompt and navigate to the directory where you want the googletest repository to exist (On Windows, I created a new directory for repositories, called C:\Users\Jeff\Documents\repositories, which I then cd’d into)
   2. On the command line, type
      git clone https://github.com/google/googletest.git
2. Set an environment variable called GTEST_DIR to the path of the new “googletest” directory that was just created by git clone.
   (On Windows, to reflect my own googletest path, I set GTEST_DIR to C:\Users\Jeff\Documents\repositories\googletest. You should set GTEST_DIR as a permanent environment variable, which on Windows you can do via Control Panel > System > Advanced system settings > Environment Variables… then “New…” under System variables. If you still have the command window open, you’ll need to relaunch it in order to use the GTEST_DIR variable.)
3. If you don’t have CMake, download and install it.
4. For an expanded version of this final step, see Building Google Test as a Standalone CMake Project.
   On the command line, navigate to a directory where you would like to place a new build of Google Test. On the command line, type
   mkdir mybuild
   cd mybuild
   Then if you are on Unix or OSX, type
   cmake -Dgtest_build_samples=ON $GTEST_DIR
   If you are on Windows, type
   cmake -Dgtest_build_samples=ON %GTEST_DIR%If you don’t want any of the google test sample projects, you can omit -Dgtest_build_samples=ON from the cmake command above.

You should now have Google Test built on your system. To go from here, if you are using Visual Studio, I’d suggest continuing on to read Google Test projects in Visual Studio. Otherwise -and in general- I’d suggest reading the Google Test documentation.