In general, GoDaddy have not integrated Let’s Encrypt, and if you wish to use it, you will need to issue and install the certificates manually in the Plesk control panel.
Whether you are able to do this or not depends on what exact GoDaddy plan you are on.
You can manually issue certificates in your browser using services like ZeroSSL.com and then uploading the resulting private key and certificate to your Plesk control panel.