Hi i have a hosting at GoDaddy, and a domain at Instra. Both has their own name servers, what does this mean?
I understood from your answer that you only have one domain, based on that:
Ask godaddy which namerserves you should use with your hosting account.
Go to Instra and change the dns's to the ones you've received from godaddy.
Wait 48h for dns propagation (probably much, much less) and go to your site.
if domains are like telephone number listings, then nameservers are like directories of telephone numbers
nameservers basically host a number of domains to point the domain to the relevant ip where your website is hosted. many companies have there own nameservers because they probably have some other service through in, eg your domain registrar provides them so you dont have to worry about nameservers or so you can just forward domains if you preferred, others like godaddy have them for hosting which allows them to manage most aspects of your hosting and its IP's automatically
unless you understand and know how dns makes the internet work at the core basics then i would simply suggest changing the nameservers to the company that hosts your website, that way they can manage the complexities automatically for you