Assuming your domain name is registered with nativespace, you can change the nameservers in the 'Domains' section of the client area https://www.nativespace.com/clients
1. Login to the client area and choose domains
2. Click on the row for the active domain you wish to modify
3. Choose Nameservers from the left menu
4. Modify the nameservers and click save.
Please note it may be a short while before the changes are visible (often 24-48 hours). (During this time, your old nameservers may still be displayed as this information is presented live from the registry - please do not submit more than once as you will most likely resubmit the old nameservers).
If your domain is registered elsewhere (and not with nativespace), you will need to contact your provider for information on how to modify any details relating to it.