How to setup duckdns domain with cloudflare?

Hi,
Im trying to setup a Duck DNS subdiomain with cloud flare so that I can enable remote access (and subsequently connect Google Assistant, but that’s down the road a bit).

I don’t know much about the web networking part and am really struggling to know how to correctly configure the domain in cloudflare. A lot of the instrcutions I’ve seen skip over this part, e.g. saying something like “add your domain in cloudflare”.
I could really do with some help for this basic step!

I have a DuckDNS account, and created a subdomain name {mysubdomain}.duckdns.org.

What I have done so far in the cloudflare UI:

  1. Click “Ads site”
  2. Enter my duckDNS subdomain
  3. Cloudflare lists a bunch of A records of random other subdomains, like for img
  4. … what next?
    according to the internet It seems to be something to do with nameservers or CNAME records or some such… but I have no idea how to do that with DuckDNS… noone actually explains the how (like exact steps in exact tools/sites) anywhere that I’ve found so far

Please help!
Many thanks in advance