Open Launchpad on your Mac system and go to the Others folder
Open Keychain Access
Click on Login and then on My Certificates
Click on Keychain Access > Certificate Assistant and open Request a Certificate From a Certificate Authority
You will now see the Certificate Assistant window on your screen.
Enter User Email Address, Common Name
Choose Select Saved to disk and click Continue
Add a unique name for your certificate and click on Save
Your Certificate Signing Request has been created