I had this problem too. I used this video to show me how to get the back off my D5300.
HOW TO DISASSEMBLE NIKON D5300 CASE COVER
by XianTek TV
https://www.youtube.com/watch?v=6DyfrvjWqEg
I only needed separate the back cover.
I found the ribbon cable just to the left of the eyepiece. It ws visably loose. I was able to take angled needle nose pliers to put it back into position and then a thin spatula to put the ribbon cable lock back down. I still need to attack all of the screws, but my camera is taking pictures again, and this saved me over $350 for a replacement D5500 off eBay. :-)