Use SSL certificates from let's encrypt in Keycloak and Spring Boot

I want to use Let’s encrypt in order to have a valid test certificate but I have some questions. I installed reverse proxy using this tutorial: How to use nginx as a reverse-proxy with letsencrypt · GitHub

After installation this added the following lines into nginx and the setup is up and running:

ssl_certificate /etc/letsencrypt/live/; # managed by Certbot
ssl_certificate_key /etc/letsencrypt/live/; # managed by Certbot

Can I manually copy/paste these certificates and use them with Keycloak server? I need to use a valid SSL certificates also for Spring Boot microservices which will communicate with Keycloak. Do I need to manually import these certificates into JVM keystore or there is no need? If it’s not the proper way how I can implement this?