how to aply sectigo ssl?

Hello.

Are ALB etc. set?
If you are using ALB, you can use it by importing the SSL certificate you purchased into ACM and setting up an HTTPS listener.
https://docs.aws.amazon.com/acm/latest/userguide/import-certificate.html
https://repost.aws/knowledge-center/elb-redirect-http-to-https-using-alb

If you are not using ALB and have direct HTTP access to EC2, you need to configure HTTPS in the web server (Apache or Nginx) settings.
Upload the SSL certificate to EC2 and reference it in the web server settings.
If you are using Apache, the configuration file in the following document may be helpful.
https://httpd.apache.org/docs/2.4/ssl/ssl_howto.html

For Nginx, the settings in the following document will be helpful.
https://nginx.org/en/docs/http/configuring_https_servers.html