In order to get the sounds to be in sync with the actual footsteps you would need to edit the sound in an editor so that you have what is called a oneshot. So just a single footstep then in unreal you would need to use animation notify events.
So basically you go through the animation and slowly scroll through the sequence to find the exact time the foot hits the floor then add an animation notify event. Play sound notify one. You would need to do this for each foot everytime it touches down in the run animation loop.