The analog inputs read voltage. You have a resistor, it won't generate any voltages - if you just plug it into analog inputs they will be floating (but coupled to each other). A floating input will read random junk from the electrical environment around it.
You firstly need to connect one side of the resistor to a reference voltage, such as GND. Then you need to pass a current through it so that a voltage (proportional to resistance and current) is present across it. Then you can measure this voltage with an analog input.
So connect one side of resistor to GND, the other to a (just guessing here) 100k resistor, other end of that resistor to +5V. Now also connect the junction of the FSR and 100k to an analog pin. You now have a resistive divider using the FSR as the lower leg - increasing the pressure on the FSR should reduce its resistance and thus reduce the reading on the analog pin.
100k is just a guess, you might have to experiment a bit.