jailbreaking iphone 4 4.2.1

[smi2710]

I know search!!! well I did and then I googled and I am lazy

can I jailbreak from my phone or do i need to download green poison to my mac to do so .

show me the links needed
thanks

 

[E_Sini]

Have to download the program to your computer. Not like android! Lol. And to do it go to the hacking section here and look at the posts that say how to jailbreak.. It goes into detail and one even had a video I think