Attributes and Date/Times of files and folders can be changed from the Change attributes dialog.
Select the files or folders whose properties you want to change, then select "Change Properties (Attributes/Time)..." under the Tools menu.
Multiple files and folders can be changed at once. It is also possible to change all the files in folders and sub-folders.
Each attribute checkbox can have one of 3 states:
If Unchecked, the attribute will be turned off.
If Checked, the attribute will be turned on.
If Blocked (as 'Archive' and 'System', seen in the image above), the attribute will not be changed: the current attribute will be kept.
If you hold down CTRL and Double Click in the date or attribute column for a file/folder, the Change attributes window will be shown, but only for that file/folder, even if multiple files are selected.