More about using Split-Tracks  
(from http://churchfront.com/blog-churchfront/how-to-get-started-with-a-click-and-backing-tracks-for-your-worship-band)  

First, you are going to need a device that is going to play your click and backing tracks. If you are a beginner, the simplest device to use is a laptop, iPhone or iPad.  

The cheapest piece of gear to split the signal coming from your phone, tablet, or laptop, is this 3.5mm TRS to dual quarter inch cable you’ll find on Amazon for five bucks. You’ll plug the 3.5mm TRS end into your device and then plug the red and black quarter ends inch into two separate channels on your mixer. The Red will be the right channel containing the backing tracks, and the Black will be the left channel containing the click. If you would rather have your phone on stage, then you will need a stereo DI box which you can plug the dual quarter inch ends into, and then out of the box you will have two XLR cables that run to your stage snake and then to your soundboard.  

Now that the signal from the smartphone is at the soundboard, you need to send the click and backing tracks to your musician's in-ear monitors.