Other than the "Modern" interface in Windows 8, there are not very many functional differences from Vista or Windows 7.
Presuming that you've already accessed Folder Options in the Control Panel and made it so you can see and modify hidden files and folders, and presuming that your Windows 8 computer account has Administrator privileges, navigate to the Runes of Magic data folder in your My Documents folder and...
1. Right-click on the RoM folder
2. Select Properties from the context menu
Look for Attributes (bottom half of the window in the General tab). For my RoM folder, the Read-only checkbox is colored in. This is one of three settings you can have for the checkbox. The others are a checkmark (full read-only status, the files in the folder absolutely cannot be changed) and blank (write access). You should be able to click on the box to change it. Change it to either colored in or blank, click Apply, and close the properties window.
Hope this helps.