1. Go to Steam, right click on Hoshizora no Memoria, then Properties. Click local files, and then Browse Local Files. It should look like this:

2.  Open the rar file, and it should look like this:

3. Open the system directory in the .zip, and you will see this:

4. Copy the files from that to the folder in Step 1

5.  Click to confirm the file overwrite

6. You're done!