1. Install OpenSSH and Winterboard from Cydia
2. Install either:
Cyberduck -
free, but needs OpenSSH
or Transmit -
almost same as Cyberduck, but it's shareware and needs OpenSSH as well
or Phoneview -
doesn't require OpenSSH, works like file browser i.e. Finder, you can copy sms/notes/music/contacts/pics/files etc to and from iPhone, but it's shareware
I use Transmit and Phoneview, just personal preference...
3. Enable Wi-Fi on your phone and note the ip address of your phone, either manually keep your phone from going to sleep or use KeepAwake toggle in SBSettings
4. Start SFTP session (port 22) , use your phone's ip address to connect to, user: root
pass: alpine
5. Navigate to var/stash/Themes.*****
Theme folder usually has random letters/numbers after word "Themes."
6. Drag and drop folder "Retro Apple Signal Bars" into Themes.***** folder
Now just select Retro Apple Signal Bars in Winterboard..After you exit Winterboard by pressing Home button on your phone, it will respring and show new signal bars...
P.S. If you're new to the whole process, it might be easier to just install Phoneview, enable advanced mode in Phoneview's prefs, navigate to to Themes folder and drag-n-drop Retro Signal Bars into it...