First install git via https://git-scm.com/download/win

Also, install Gpg4win via https://www.gpg4win.org/

After installing Gpg4win, you can import secret key using GUI tool Kleopatra.

Check your GPG signing key using following command

gpg --list-secret-key --keyid-format LONG

You will get following result

------------------------------------------------
sec   rsa3072/XXXXXXXXXXXXXXXX 2020-08-01 [SC] [expires: 2022-08-01]
      AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
uid                 [ultimate] MyeongGeun Shin <mg.shin@kaist.ac.kr>
ssb   rsa3072/BBBBBBBBBBBBBBBB 2020-08-01 [E] [expires: 2022-08-01]

The XXXXXXXXXXXXXXXX part will be used for specify your secret key.

Now execute git config --global user.sigingkey XXXXXXXXXXXXXXXX.

You must check where gpg has installed using

> where gpg
C:\\Program Files (x86)\\GnuPG\\bin\\gpg.exe

Then, execute git config --global gpg.program "C:\\Program Files (x86)\\GnuPG\\bin\\gpg.exe"

Now it's all done! :)

If you want to sign your commit, you must enter

git commit -S