While filing the state where I live (Pennsylvania) I am asked about taxes paid to another state. I only earned in another state (Delaware). Why does it say $0?

You should enter your W-2 as it is shown.

Also, you need to file two states tax returns.

You should be filing a resident (PA) and a nonresident tax return (DE).  You should enter your nonresident state tax return first.

It is recommended to prepare the nonresident state first because your resident state will provide you a credit for the tax you pay to the nonresident state.  By preparing the nonresident state first, TurboTax can transfer the credit information to your resident state to return.  

So this should be calculated for you.

Click here for instructions on how to file your nonresident return.

Click here for information regarding filing multiple states returns.