Hi,
I'm not entirely sure what you are trying to achieve here?
If you want a new domain name for your website then you should redirect the old domain to the new one which contains the new site. For that you would do a
301 permanent redirect.
If you are trying to improve your websites rankings in Google for example then simply registering another domain and then linking it to your current domain will have zero positive impact for you.
Instead, if you are trying to increase your rankings you need to gain link partners with Websites that are of a similar topic to your own. By creating good quality content you can attract links to your site because people will want to link to good content. Other ways are recipricol linking.