How do I rewire this box?
First, you can only connect one wire to a screw. If you need to connect multiple, then you create a pigtail by cutting a short piece of wire and attaching one end to the screw, and the other end is connected to the other wires with a wire nut.

Second, you need to figure out which cable provides the power to the box. Most likely it is the cable without the red wire.

Once you know which cable provides the power, then any black or red wire you want powered all the time gets connected to this black wire with a wirenut. You should also pigtail this wire to one of the terminals on your switch. Any red or black wire that you want controlled by the switch should be connected to the other screw of the switch, with a pigtail if necessary.

In general, ceiling lights with black and red wires are wired so that the black wire is for a light and the red wire is for a ceiling fan. Similarly, the black wire to an outlet typically provides continuous power, while the red wire is connected to a switch. In either case, if the red wire is unused, then you should wirenut both ends.