Get the New Nameserver Values from your Hosting Provider, they often look like this: 

• ns1.dns-parking.com
• ns2.dns-parking.com 

NOTE: Write down of all these addresses because you’ll need to enter them into your domain registrar’s control panel.

A.) Login to your domain name provider/registrar. Remember, this is the place where you bought your domain.

B.) Look for the option to set your domain’s nameservers. Every registrar has a different way of doing this. However, in general, you can find the appropriate settings on the menu called Domain Management, or Domain Overview, or something along the lines of 'management page' 

C.) Go to the “Manage DNS” page of the selected domain name, Scroll to “Nameservers”, You should see several fields, such as Nameserver 1 (primary nameserver), Nameserver 2 (secondary nameserver), that will most likely be filled with the default nameserver.

D.) Click the Change button next to where it says, “Using default nameservers.” Choose the Custom option; not Default. Then enter the nameservers into the appropriate fields. For example, a nameserver that begins with ns1 should be put into the Nameserver 1 field, if it starts with ns2 to Nameserver 2, and so on. Click Save and you’re done.

*Alternatively, you can ask your Domain provider's Customer Support to add the new nameservers for you.*

Once the nameservers are set, you need to wait for the changes to take effect. This period is referred to as worldwide DNS propagation.

The process usually takes a few hours, but it can also last up to two days. 

You can read a more detailed blog article with diagrams Here