This post assumes you’ve already read Generating a PGP key.
I’ll be using my key for these examples but you’ll want to replace 95535225B55B5A9F39E29F5EDAB85EABB6014D3F
with your own in the commands.
git config --global user.signingkey 95535225B55B5A9F39E29F5EDAB85EABB6014D3F
git config --global commit.gpgsign true
This will automatically sign all of your commits with the key you added to user.signingkey
.