how do you tune your violin with a piano?

Question

my violin is really badly untuned , i have a piano but i have no clue which key to press.
help please

Answer 1

First off, it's best to find middle C. You know how there are black and white keys? Well, where there are two black ones, the white key right before the first one is C. They go up from there [on the white keys] up until the note G.
A violin's strings are E, A, D, G.

Answer 2

You can use the piano to tune to the A440, which is the A above middle C, which will work if the piano is in tune.

There's a free tuner online. See:
http://beststudentviolins.com/StringCareSpecs.html#9

...scroll down a bit.