Google search console and change of domain name

I’m new with WordPress and all things SEO. I originally had a free domain and added this to Google Search Console. I then upgraded to a custom domain and added this to Google Serach Console. I thought since they are technically different URLs with a redirect, I could have both. But it seems like I can’t because the only pages that have indexed on the custom domain are no longer indexed on the previous domain. Should I just remove the previous domain and hope GSC indexes everything on my new custom domain? Was hoping not to lose my previous analytics but don’t want ongoing issues. Thanks!