In order to modify your nameservers on a domain name purchased through DreamHost you can follow the steps below: 

Using the Manage Domains page to make a change

One of the main pages you will be accessing for the management of your domains hosting is "Panel > Domains > Manage Domains":

1. Under the domain name you wish to edit, click the "DNS" link
2. Erase the nameservers listed in each box and replace them with the nameservers provided by Fused. The Fused Network shared hosting nameservers are available within your cPanel beneath "View Cloud Nameservers." Each domain name hosted with us will have a unique set of four nameservers you'll need to enter at your registrar
3. Click the blue "Set these nameservers for example.com"! button to save your changes

WARNING:

When changing nameservers, you will be manually repointing the domain. You are responsible for the outcome of these changes. If you have further questions unanswered by this article, contact support at support@fused.com