What can I do to prove my innocence after being found guilty for rape and kidnapping?

File an appeal.

First you need to file a notice of appeal within the prescribed time after entry of judgment. In Washington 30 days. You have more right to raise a full range of issues in direct appeal. If you are still within the appeal period you may also have a right to ask a new trial. If you have already passed the appeal period you there are other remedies that have potential, e.g. habeas corpus. In all of these potential course you should consult with your attorney (which for this level of criminal matter you should have had).

You say, you have already been found guilty. In this case, it may be tough. I can't say without seeing all the records and reviewing the trial transcripts.

There maybe something from the case record that can get your conviction overturned or get you a new trial. This cannot be accomplished without having an experienced appellate attorney thoroughly review your case record for anything that can get it back in court.

Hire an attorney.

You can appeal the case or you can run a 440.10 motion if your lawyer (I assume you had as public defender) was "ineffective" which is a very difficult standard to meet. Most people who are convicted of serious charges are in fact guilty and the evidence is overwhelming, but they refuse to admit their guilt or take a plea. That results in a long prison term because they lied to their lawyer and insisted on going to trial. Sometimes people are innocent but are misidentified or falsely accused. In that case they need a very good criminal lawyer to show that the witness is either lying or mistaken. You should tell a good lawyer the truth and let him look at the case and see what can be done, but if you are not totally honest with him there is no way he can make good decisions or help you in any way.

Appeal the verdict.