Aucist Others give up, I insist
On Yahoo Domain Control Panel, we should unlock the domain, then can change DNS. Click "Edit Domain Locking", as below. Then follow the tips on the web page.
Make sure "Your domain is currently unlocked". Then click "Manage Advanced DNS Settings", click "Change Nameservers", as below:
I strongly recommend a very good free DNS he.net, you should register an account on https://dns.he.net, one account can add 50 domains, the brief usage you may view this I wrote: http://www.aucist.com/emboss/4, then you should add a new domain on the panel of he.net. On Yahoo Panel, input NS1 and NS2, as below:
After change Name Servers, you should lock your domain.