Go to your App Store purchased history. If you previously owned an app, Apple will often offer to download the "last compatible version" for iOS 6.
Before starting, ensure you have:
Downgrading iOS firmware carries inherent risks. Read these warnings carefully before proceeding: downgrade ipod touch 5 to ios 6
The downgrade tool needs a network bridge to communicate deep instructions to your iPod. Open on your iPod Touch. Search for OpenSSH and install it. Go to your App Store purchased history
This process will wipe data or require fresh partitions. Back up your music, photos, and files before starting. downgrade ipod touch 5 to ios 6
You cannot restore a stock IPSW. You must create a custom IPSW that includes your saved SHSH blob.