If you didn't use a custom domain (by letting the field "Custom Domain" empty), your automatically allocated domain is already setup for both http and https access.

If you used your own custom domain for the frontend, after you finished the steps above, you can only use http to access your website. That is http://xxx.yyy.zzz, if you want to enable HTTPS on your domain, you need some extra steps.

In order to enable the https access, aka https://xxx.yyy.zzz , you need a HTTPS certificate. Many companies can provide it to you. Here we are going to use https://letsencrypt.org/ because it gives you HTTPS certificate for free (but the certificate is valid only for 3 months so after 3 months you should renew it).

Let's go back to your VM. First you need to install certbot (the tool provided by letsencrypt), which can be downloaded and installed by apt command (apt intall certbot). Then execute the command.

Note that if your service is not a WordPress, you will need to find the directory where certbot can put a file that is accessible through http://xxx.yyy.zzz. If you have any problem, please read the FAQ from letsencrypt (https://letsencrypt.org/docs/faq/). 

Once certbot has run successfully, you will get two files: /etc/letsencrypt/live/xxx.yyy.zzz/fullchain.pem and /etc/letsencrypt/live/xxx.yyy.zzz/privkey.pem

In your frontend service, there are fields "[DEPRECATED] SSL Certificate" and "[DEPRECATED] SSL Key". Put the certificate ("fullchain.pem") content in the field "[DEPRECATED] SSL Certificate" and the key ("privkey.pem") content in "[DEPRECATED] SSL Key".