Question

how does using a ramp make lifting a heavy object easier?

Answer 1

Here's an example where the box is going to move the same vertical distance (typically what you would use a ramp for). You can either exert a force to dead lift it, or you can exert a force along the incline of the ramp.

Either way you're going to do the same amount of work. But a ramp allows you to exert a small force over a longer distance to the job. In a dead lift, you have to exert a force equal to mg over the height you're lifting. With a ramp you only have to exert mgsin(theta) the distance of the hypotenuse