Open Knorish dashboard integration section as given below, fill the details and click to create.
After creation you will receive a message with nameservers which you need to use on domain registrar website, here's a sample.
You may have received email from Cloudflare which will have these details too, here's a sample.
Once you added nameservers on domain registrar website, you need to wait around 24 hours to see custom domain working with free SSL certificate.
If you are not able to access your Knorish website from your custom domain (after 24 hours wait) then login to Cloudflare dashboard.
Check #1. Check domain/website status is Active on overview page, here's a sample.
Check #2. Check that these two CNAME preset on DNS page, here's a sample.
Check #3. Check that SSL certificate is issued and it's status is "Active Certificate".
Check #4. Check that SSL certificate is set to "Full" (select that in drop down).
If you are still not able to access your website with custom domain, we recommend to disconnect using Knorish dashboard and connect again, after that verify above 3 checks meets.