Setting up IMAP is basically the same as setting up POP.  The only real difference when setting it up is the incoming server ports.  Most clients will automatically set the port based on whether you choose IMAP or POP in the beginning of the set up.

Here are the instructions to setup IMAP:  How to set up POP and IMAP

NOTE: IMAP is available to users with the following packages:

• Web Hosting Large and Unlimited
• nsCommerce™ space - All Packages
• nsHosting™ VPS - All Packages
• nsMail™ Pro

IMAP offers you:

• Compatibility with Internet messaging standards, such as 'MIME'
• Access to your messages from multiple computers
• Access to messages without having to download from the server or transfer messages from one computer to another
• Support for "online", "offline", and "disconnected" access modes
• Support for concurrent access to shared mailboxes

Related Articles

The Differences between POP and IMAP

What is IMAP?

Mail Setup Videos