How can I change from from Bitcoin to Ether?

If I have BitCoin and I want Ether, how do I do it?

Firstly, you will have 2 wallets

1 for BitCoin
2 for Ether

Take the Public Keys for both and go to ShapeShift

You will see an option like this:

Choose the currency that you want to send and the one you want to receive:
For example:
Bitcoin and Ether

Press continue and the following page with appear:

Enter the Public key for your BitCoin.
Enter the Public key for your Ether.

Notice the Minimum and Maximum Fees and the Exchange Fee.

Then, if you are happy with what you see, start the transaction!