Install themes using iPhone Explorer

To be able to access the root directory of your iPhone without using wifi, you need to download iPhone Explorer. It's a free app that is the equivalent of Winscp for people with wifi connection. With this, you just need an iPhone usb cable. 

1. Download iPhone Explorer from Macroplant.com.

2. Install it on your computer. 

3. Plug the phone using the usb cable. 

4. Assuming you already have the folder of the theme you just downloaded, just copy and paste it on the themes directory of the iPhone located in Root/Var/Stash/Themes

5. Once done, open Winterboard to install the theme, select then Respring.