Show hidden files and go in your home directory to get the .Wine folder. Open older, go to drive_c in windows and then create a folder "Resources". Finally create a folder "Themes" and create another folder that will bear the name of your theme
Extract and paste the contents of the zip or rar file into it.
Installing the theme
Then Launch Wine, and open the "Integration with Office" tab and then click Install a theme. Browse inside, and look for the file .msstyles file. In the theme menu (near the install a theme button) select the desired theme.
Apply, and you'll have youre customized version of the software.