Multiplying the voltage output
Assuming the 0-5 Volts is supposed to switch the output, in which case you want a program to control your output, then you will want to use a digital output pin to either switch a relay or a transistor that controls the 10 Volts put out to whatever it is that you are controlling.  

Perhaps you want PWM which indicates a transistor circuit.  Hard to tell what you want from the way this is worded.

Taking your words literaly, "I need the output to be 10V always" then that simply means hard-wiring to a 10V power supply.   ;-)