If you would like your site's address to redirect to another address, you can do this by accessing your Advanced Domain settings and following steps from this tutorial: Assigning Domains and Creating a Primary Domain.
However, you would need to make sure that any externally purchased domains are pointing to Yola before you can do this.
If you are trying to add a 301 redirect for a specific page on your site, unfortunately, we do not have a feature on Yola that you can use. An alternative would be to create that page, make sure it's not included in the menu and then add a snippet of HTML that will redirect your visitors to another page. This tutorial will explain how to do that: Links that redirect when you click on a menu tab