This is a little tricky, since I don't have a clue what you are doing!
But what the hell. I'm going to assume that you are dropping a resistor into a simple circuit. If it's a complicated circuit, go do some research before doing anything but this will get you started.
Amperage is measure in amps, voltage is measured in volts and resistance is measured in ohms.
Amperage = Volts/Resistance
The rest is math (and making sure you've got the right color-coding on the resistor....that part is darned important too!).