Help connecting a source directly to an amp

A month or so back, I posted a question for a friend who had just picked up some massive, DIY speakers. They were free, and this is his motif: get sound, enough to enjoy and dance to, for as little money as possible. (Let's agree he's a budding audiophile.) He now has picked up an amplifier, also free. I think it's an amp for DJing, although I think that his friend also used it to plug in a guitar and wail. 

He's hoping to connect his source (an iPhone or laptop) to the amp without the nuisance and expense of a pre-amp. The inputs on the back of the amp are balanced/XLR and ... what looks to me like a pair of 1/4" TRS jacks. As you can tell, I've never done this and simply don't know the basic electronics. 
So: is there a way to connect an iPhone directly to either XLR inputs or (what looks like) 1/4" inputs? 

Here's a picture of the inputs on the back of the amp:

https://imgur.com/pu13uQJ

And just because it's such a fun picture, here are the speakers that he picked up:

https://imgur.com/F09UqrQ

I know this isn't exactly a high-end audiophile question but I hope y'all appreciate the spirit of my friend's quest for music! He and I are ready to be schooled. Thanks!