You will be transferring through KWI on only one airline, so your baggages will be checked through all the way to FRA. Make sure that you receive the boarding passes for both the legs as a confirmation. When you land in Kuwait, simply follow the signs towards Transfers. T4 is a pretty new and a small terminal so you'll be having a good experience! There's Starbucks and plenty of other restaurants here or you can pay to access the AlMubarakiya lounge (KD10 or 15, I am not sure about the price). Safe travels.