You can download the update directly on your Windows 8 or Windows RT device through the Windows Store or by using the link which follows:
The Yahoo Mail! for Windows update has the following new features and improvements:
- Integration with Dropbox: allows you to share and store files more easily. Since files can be stored in your Dropbox account online, it's easy to find the files you want even when you are away from your desktop.
- Multiple Accounts enhancements: ability to Sign out per account or of all your accounts at the same time
- Overall performance enhancements and bug fixes