How to change certificate after default Meet installation

Hi All,
I have set up a Ubuntu 20.04 server with a default Meet install; Jetty Web server ( I believe) and self signed certificate. Meet working but browsers are generating security warning because of self sign cert. I followed steps to generate a letsencrypt wildcard SSL using certbot (with autorenew) and that appears to have worked as I can see the cert files in /ect/letsencrypt (although they are all .pem which I have not used before). However I am entirely stumped at how to apply this new cert to Meet. If you can assist please can you address your response to a linux newbie - I am from the MS world and have only a basic familiarity with Linux configuration.