can i put the receiver battery right behind the firewall
It's good practice to keep all radio components away from the engine. The plug sparking can cause havoc with the radio signal. However; resistor plugs, and/or plug wire shielding, and the firewall spacing is usually enough.

also where do you connect the switch.
There is a lead (not the spark plug lead) coming from the coil. Connect this to one side of a SPST switch. Connect the other side to the engine crankcase. When this switch is closed, it grounds the primary side of the coil, preventing the engine from starting.

also how do you install the fuel lines on the tank,
Gas engines use pumper-type carbs and do not need gas tank pressure. Connect the supply line from the tank to the carb. You can tee this off to a fueling valve if you desire. Run the gas tank vent tube out of the fuselage and to the bottom of the plane. It remains open and unconnected.

Dr.1