Trying to incorporate Jitsi Meet Api into my Web Platform

Hi, I am a new JS coder and I have been trying to incorporate Jitsi Meet as the main video calling system in my web platform. I don’t know how to get 2 separate users on the same video call only using the API. I also have no idea on how to keep a user on one video call instead of generating different meetings even if they refresh or exit the page.

<a id="start">Click here to start the meeting</a>
<div style="margin-top: 20px;"id="jitsi-container">
              <script>
                var button = document.querySelector('#start');
                var container = document.querySelector('#jitsi-container');
                var api = null;

                button.addEventListener('click', () => {
                    var possible = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
                    var stringLength = 30;

                    function pickRandom() {
                    return possible[Math.floor(Math.random() * possible.length)];
                    }

                var randomString = Array.apply(null, Array(stringLength)).map(pickRandom).join('');
                    var domain = "meet.jit.si";
                    var options = {
                        "roomName": randomString,
                        "parentNode": container,
                        "width": window.innerWidth -20,
                        "height": window.innerHeight ,
                    };
                    api = new JitsiMeetExternalAPI(domain, options);
                });

                </script>
<script src='https://meet.jit.si/external_api.js'></script>