[sir-understeer]

Ok, here's what you need to do.

Make sure the intake fan(s), usually in the front, is sucking air from the room into the case.

From there, the cooler fresh air will need to make their way to the GPU, PSU, and CPU fans, as they all have fans that are designed to suck the hot air away from the processors. Those fans will need to get that hot air out of the case efficiently, usually out the back of the case and on the top (hot air going up, yada yada yada). If the case was designed well, it might even have a couple of fans on the side of the case, "on top" of the CPU and GPU area (if you lay the computer down on its side, so that the motherboard is sitting horizontally) that will help suck that hot air out.

From what you're describing, all the air is being sucked into the case and there's not exhaust, thus the air that's in there just keeps getting hotter and hotter, since there's no fresh cool air entering the case.

If you can, just take the side panel of the case off for now, as it will allow the air to escape the computer chassis, but if you want the side panel on there, you must fix the fans, and make sure the path of fresh air will reach the critical areas of the case.