Without SSL your browser throughs insecure connection error for your users, to avoid this you need to add an SSL for your Custom Domain since you’re using the only domain without hosting you cannot add let’s encrypt SSL or any other premium SSL, the best solution is using Cloudflare CDN.
Follow these steps to add an SSL certificate for your Custom Domain.
Step 1: Create an account on Cloudflare.com
Step 2: You will receive an email link for activation, after activating your Cloudflare account, the next step is to add your site.
Step 3: Click next.
Step 4: Select your plan (FREE plan) and click confirm a plan.
Step 5: DNS query results for your domain will be shown, click continue.
Step 6: Change the default nameserver of your domain to Cloudflare nameserver.
Step 7: Click continue and wait for DNS propagation, it may take up to 24 hours but in most of the times takes less than an hour, so please be patient, after DNS propagation your site will be visible on Cloudflare dashboard with a green tick mark as Active.
Step 8: Now select your site and go to Crypto settings, here you need to select the flexible option from the drop-down menu, and also don’t forget to enable both “Always Use HTTPS” and “Automatic HTTPS Rewrites”, wait for a couple of hours to activate your universal Cloudflare SSL.