Update existing WP site from Http to https

We have an existing website and need to change it over from http to https.

The site runs on AWS and according to AWS Support everything is setup correctly ie. SSL certificate, load balancer, etc.

The last thing to do is to change all files, etc from http:// to https://

Most of the articles we have found are over two years old, so we want to ensure we have updated information.

And, we have backed up our site before going through the process.

My understanding is that we have to make the following change in the wp-config.pho file:
define(‘FORCE_SSL_ADMIN’, true);

Should be also change in the wp-config.pho file the following:
http://example.com replace: //example.com
replacing http:// with simply //:
and should be include the URL name

In General/Settings, we are unable to change the URL from http:// to https:// as it is grayed-out and cannot be changed.

How do we make the change required in General/Settings for the site name, etc

Is there a plugin that will make the changes?

Any valid procedures that are up-to-date that we can review.

Thanks so much for any responses.

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