Justhost nameservers are:
ns1.pipedns.com
ns2.pipedns.com
ns3.pipedns.com
At your current domain registrar you should put these namerservers in order your website to be hosted on justhost. After you apply the nameservers there is a typical 48-72 hours propagation until all DNS servers worldwide are updated.
Nameservers and DNS
Nameservers are part of the so-called Domain Name System (DNS for short). They are responsible for mapping IP addresses to domain names. Humans invented this system because numbers are hard to remember. Instead a names are very easy to remember. That it is how the .com era begun. Only two nameservers are required for each domain but there can be more. These are called authoritative nameservers, ones that are responsible for certain domain name. Once a domain name is resolved the application (internet browser) connects to the web server and request the page. Once it downloads the page it renders the code and it shows it to the user.