Open up iTunes. Make sure it is running!

Now click wiNstallerGUI.exe from the package downloaded previously.

Click 'Activate' and it should activate the phone as well as jailbreak it.

Wait for all the coding lines to be complete. You should have the 'Activate iPhone - Connect to iTunes' screen on your iPhone when it has finished. 

The last few lines should be:

Sending public key
Deactivating
Deactivate succeeded
Activation succeeded
Jailbreak complete!

Then hit 'Install Application' and navigate to the Installer.app (NOT the webplugin folder) folder inside the first wiNstaller folder in the downloaded pack. You should now have a 1.0.2 phone with the 1.1.2 modem firmware but is now activated, jailbroken, and have installer installed.

Slide to unlock, then connect to Wi-Fi. Set Auto-Lock to Never.

Tap Installer and update it. Install Community Sources, then BSD Subsystem, and then OpenSSH (Both are in the 'System' subfolder).

Reboot your iPhone here. 

On your computer, install WinSCP and open it. Note down the IP of your iPhone (Settings > Wi-Fi > Blue Arrow next to your Wi-Fi source).

In WinSCP for the host name type in your IP for username type root and for password type dottie. Log in.