Hmm, it is basic computer knowledge.
You can not paste file on file In addition, you have to distinguish the file from the folder.
In Windows you need to have hidden and system files displayed. Unpack file from archive, you got "system". Right click on it - choose copy.
Then, right click on empty space near "system" file in the device memory (or sd card, or both), then click paste.
Windows will ask if you want to overwrite it, and if you are sure, confirm.

Of course, first of all - backup. Backup current "system" file in safe place in your PC.