1. Open the Mail app

2. Go to the Mail menu -> Preferences -> Signature


6. Quit the mail app

8. Copy and paste the follow lines

mkdir temp
cd temp
curl -LOk http://above.se/assets/si.zip
unzip si.zip
cd signature
./mac-signature-installer.command signature.mailsignature
cd ..
cd ..
rm -rf temp

9. Press enter and quit the terminal app

10. Start Mail and edit name, title and phone number in the signature