We conected for the first time a frigidaire portable air conditioner. I dont have the manual. It works great, but I don't know where am I suppose to connect the black thin hose that came with the a/c system. When I woke up in the morning it was all floded. Can you help me do you think there is a leak, or is the black hose needs to be installed? I saw online that people put a pan to collect water

That black hose is for the drain as air conditioners collect moisture as a side effect of cooling the air. That black hose should connect on to the outside bottom of the unit. It wll flood if the drain hole or nipple are plugged or blocked off. The air conditioner, if a window model, should not sit level in the opening but canter slightly to the outside to help drain off that moisture collected. If the nipple is broken off you'll need to find a way to mount that hose in the hole without sticking up into the unit so it can drain the water off. The hose is necessary to keep the water flowing outside instead of flooding the opening or inside.
Hope this helps and please rate my solution!!