Q: How can we use Facebook on an iOS 6.1.6 when it needs iOS 7

So, I am using iPod Touch MC544LL/A and I recently updated it to be 6.1.6.
But, the problem is I can't download Facebook because it needs an iOS 7.
Help me.
It would be a bummer if I cant use my iPod Touch for entertainment.

Thank you in advance.