How do I enable disk use?

I presume since you haven't provided any details that you want to enable an iPod. Connect your iPod to your computer, when it appears in iTunes click on it's icon to bring up the preference tabs in the main pane. Check the box "enable disk use" in the Summary tab and click Apply: Using your iPod as a storage drive

If your iPod is set to update manually disk use is enabled by default.

Thank you i have had the same problem.