Replacement screen won't come alive

I have a iPhone 5c that spend 2 weeks in a muddy sump. Build a grabber and it come out covered in mud. Put it in rice for a week. Charged the battery, but the screen wouldn't light up. Ordered a new full every thing there screen. While waiting for the screen to come in, I hooked it up the charger and it came alive, but no screen. I got a message on my iPad that Dons-iPhone is using my ID for messaging and FaceTime. Installed new screen and still no access. Just a black screen. I'm an 75 year old, old MIS and radio person. This is a Challenge, any ideas?

Thanks

Don Roberts

droberts23604@yahoo.com