If your domain name is registered with KartHost (meaning you paid KartHost for registration and/or renewals) here is how to change your name servers.
NOTE: If you need to know the Nameservers for KartHost Services please review this KartHost Knowledgebase Article for the proper Name Servers: What are my Name Servers for my web site at KartHost?
IMPORTANT: By changing Name Servers KartHost to non-KartHost name servers, KartHost will no longer be handling DNS for your web site and email. Contact your new DNS provider for those details and make sure your DNS is set prior to the change of the name servers.
TIP: Because of Internet Propagation changing your name servers can take just a few minutes to propagate the internet or can take as long as 24 to 48 hours. In most cases the internet propagation will take effect within a few hours. But it’s no guarantee. So be patient. If its been more than 36 to 48 hours Open a KartHost Domain Name Support ticket.
Step 1) We will assume you are logged into your KartHost Customer Center account. If you are not logged in or need to know how to login please see this KartHost Knowledgebase Article Introduction to the KartHost Customer Center - Video Click on the black Navigation Bar click on Domains as seen below.
Step 2) On the resulting drop down menu select My Domains.
Step 3) On the resulting My Domains page find your domain name and click on the “Manage Domain” button to the far right side of page.
Step 4) Now you will be on the domain name management page for your specified domain name. When you land on the page you will be on the Information tab, and you will want to click on Nameservers tab.
Step 5) Now on the Nameservers page you will want to remove ALL existing name servers, and then replace with the new name servers. You will need to get your name servers from the party that will be handling your DNS for your domain. NOTE: If you need to add more than 5 Nameservers go ahead and add your first 5 and then open up a Domain Name Support Ticket and provide the additional name servers that need to be added in that ticket.
Step 6) Now click the Change Nameserver blue button and you will see a green band across the tabs showing successful change. 
If you see a red band across the top, there is some sort of error. And you will need to click on Nameservers tab again & double check to verify your name servers are correct.
After the Change Tip 1) The next thing you will want to do, is clear the caching for your local computer (or router). They will more than likely have cached the OLD IP address. You will want to review this KartHost Knowledgebase article “Clearing Your IP Cache on your local Computer”
After the Change Tip 2) Also you will want to check the change using an offsite Proxy Server. Roy at KartHost Recommends using anonymous.org, it’s a proxy in Germany. So it’s like actually being on a computer in German surfing the web. This helps confirm the name server change has taken affect across the globe. Just click on English to use the English version of Anonymous or Deutsch to use the German version of Anonymous.org.
If you are having any issues, please contact KartHost Customer Center Support.