Easiest way to train your ear ?

There’s no real easy way to just be able to train your ear to hear chords or notes. It would take a LOT of time, just listening to the notes, identifying them, and remembering what they sound like. There’s perfect pitch, and then there’s relative pitch. You would probably end up having relative pitch if anything. That’s where you would start with a base note, such as a C, and in your head work your way up or down the scale, knowing what each sounds like in progression until you hit the note in your head that’s being played. Unfortunately, unless you already know how, or have perfect/relative pitch, you probably won’t. It’s something your either born with or work insanely hard to try and attain it, and even then it doesn’t happen often. But that shouldn’t stop you from being able to eventually tell if say a guitar, is in tune or out of tune. That just takes time and practice. That has more to do with memory than the ability to hear a pitch in your mind. Hope that helps. Kinda. Just practice. Who knows what will happen, or what abilities you have that you don’t yet know you have capable within you.