well first question is have you jailbroken the touch?
unlike the not so helpful post above 🙄
if you have jailbroken your touch then go to installer, click sources then edit button. Now click add then a box will pop up and infront of http:// enter repo.us.to then ok and the sources will refresh.
now go to install section and scroll down to IPhone 1.1.X Apps, select the one appropriate to your firmware. in there firstly scroll to the bottom of the list and install the prep files for maps and mail THEN install the mail and maps apps.
Also please note that the Yahoo mail option does NOT work, there is a work around on the net via izymail.com 😉
if you need any help then post back and I'll happily help