1. Go to https://membercenter.msn.com/Default.aspx.
2. Sign in to MSN Explorer using your primary email account.
3. Click on Manage Users from the options available on the left side of the page.
4. Under Add a new member, click Add a member.
5. Fill out the information requested on this page and click Next.
6. Review and sign the agreement and then click Accept.
7. You have now successfully created a new secondary account.

Note: To open another email address under your primary email account, repeat the steps mentioned above.
The account you just created will be visible on the MSN Client Software when you sign-in the next time.