you have to ssh into your ipod
if you don´t know how to do it:
1.download openssh with cydia
2.download and install winscp to your computer
3.connect your ipod to your computer
4.open winscp
5. in host name, put in your ip-adress
port number must be 22
username is: root
passwort is: alpine
6. click login
7. search the downloads folder of installous (i think it was in /var/mobile/downloads or var/mobile/library/downloads,not sure google it)
8. put your ipa file into the folder and then you can install it with installous on your ipod