You took apart the hot end. I am assuming to remove to the nozzle for cleaning? There are two threaded holes in that picture. The larger one for the nozzle, and the smaller one has an L shaped bracket used to hold the thermistor in place. The thermistor goes into the unthreaded hole NEXT to the threaded hole. The thermistor wires look bent in that photo because the L shaped bracket squashes them.

Here's two links you will need to replace the insulation material.

https://www.amazon.com/gp/product/B00DVBLOQ4/ref=oh_aui_detailpage_o01_s01?ie=UTF8&psc=1

https://www.amazon.com/gp/product/B01LAYCRAA/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1

reinstall the nozzle, tightly but not too tight. re-install the thermistor and L bracket. Then wrap everything with the insulation and use the 1/4" kapton tape to hold in insulation in place.