When purchasing BOTH a domain name along with a hosting package with us (your domain may be at a different domain registrar so this article is not relevant for you), you have to keep in mind that you will also need to set up the nameservers for the domain (or ask us to do it for you which we're happy to help with).
You can do that with a few simple steps.
Firstly, you will need to find the nameservers for your account.
You can find them in the "Service Details" section of your hosting panel.

Now once you have those, head over to the "Domains" section under "My Services" and choose your domain.

Once chosen, you will be taken to the page where you can manage the domain.
You will be able to set nameservers and other records. In addition to that, you can register your own nameservers, change the contact information of the domain, turn on/off whois privacy and also setup redirects.
In this case, we will be changing the nameservers of the domain to ours (WPX).
You will be taken directly to the "Domain details" section. At the bottom you'll see the option "Manage Nameservers" which you'll have to choose.

Now simply choose the option and fill in the nameservers inside.
You get two nameserver records with us and those would have to be filled in under the fields "Nameserver 1" and "Nameserver 2" and then click "Save Changes". You don't have to worry about the "Nameserver IP" fields.

That's it! You have now set the nameservers for the domain and it should start loading shortly!
Keep in mind that if there were other nameservers previously set (not pointing to our servers), the technical time needed for a full DNS propagation can take up to 48 hours. In some rare cases it can take up to 72 hours.
More information on the topic can be found here: https://wpxhosting.com/knowledgebase/article/50/what-is-dns-propagation-and-why-it-can-take-up-to-72-hours-/
If at any point, you get stuck or aren't sure how to proceed, just raise a support ticket with us here:
https://wpxhosting.com/tickets/new/
and we'll answer ASAP.