Minimal readership means that your website has very less or no viewers at all. So you need to send viewers to your website to claim your domain.
But the problem is that Facebook needs to get those views from Facebook only (i.e. the viewers who visit your website from the links shared on Facebook). So you need to send the traffic from Facebook for about 7 days.
Daily visits from Facebook traffic should be at least 1500. That means you have get 1500 views per day on your website for 7 days to clear minimal readership.
The no of days also depends on domain extension. The domains with .com or other TLDs get approved within 10 days but some domains that use free extensions such as .tk may take more time.
After your website has cleared the minimal readership, add your website or domain under the connect your site in configuration section of Instant Articles in Publishing Tolls on your Facebook Page. It will ask to add meta tag to your website’s head section.
Do that and your website will be added. Now your URL will be checked by Facebook and it will show pending status. Send more traffic from Facebook to your website for few more days to get the URL approved.
After that you can submit your articles for review but do not add any article in the production library until your URL is approved.
10k – 12k Traffic in 1 Week ( Minimal Readership Error Solved )
After you need to follow the Approve your site Facebook Instant Article Guidelines.