IPod touch jailbreak help?

[blah]

I downloaded greenpoison for my iPod touch 3.1.3 which runs on 4.1 but everytime I download something when I open the download it just goes back to the home screen and for mywi it totally reboots my iPod but I really want mywi because I go out and sometimes I don't have wifi. For winterboard when I download it it doesn't even show up and I looked it up and it says to reboot it but when it's done downloading there's a thing that says reboot but it still doesn't show up.