You should see a picture icon, click it then enter the URL of the image (which should end in etc) then click ok and it should enter it in the toolbox.
The second way is if you don't see the toolbar, don't worry its not too hard, you just need to enter a bit of extra text.
If you want to just jailbreak i Phone 3.1.2 I recommend you use blackra1n, but if you want to unlock then you have no choice but to use Pwnage Tool which only works with Mac. If you don't see the blackra1n icon, go to the last page on your i Device and you should see it. Install your preferred aplication from the blackra1n app. If you don't know how to do that, read my jailbreak i Phone 3.1 with Pwnage Tool post which gives step by step instructions....
If you haven't already downloaded i Phone 3.1.2 or updated, the download links for it are below. You have the option of choosing Cydia, Icy, or Rock.
Pwnage Tool is an i Phone jailbreaking application for Mac OS X that creates custom i OS firmware images to user-defined specifications.
These firmware images often contain the APT interface Cydia as well as additional APT packages.
Go to the text box where you want to enter your answer, comment or question and you should see a tool bar on top of the text box with a load of icons across the toolbar.The blackra1n software is available for both Windows and Mac users, but it only supports i Phone, i Phone 3G, i Phone 3GS, and i Pod Touch.blackra1n does not support the i Pod Touch 3rd generation 8 GB models that have a MC in the model number.Before you get started with the unlock, you need to consider the following: Important notes about i OS 4.2.1 unlock on i Phone 3GS and i Phone 3G It is important that you understand and accept these risks before proceeding.If you have older baseband, you can go straight to using ultrasn0w. Tai G provides an i OS 8.4 and 8.3 untethered jailbreak.