LED- Resistor, does the position matter?

No, it does not matter. There are several cases:

• The LED works: in this case the resistor will limit the current flow, and does not matter if it is before or after, since it is connected serial.
• The LED does not work:
  • Electricity flows through the LED: it would go through the resistor anyway, either if it is before or after the LED.
  • Electricity does not flow through the LED: current will not flow anyway through the resistor because the circuit is not closed.

To light the LED, using the resistor to define the current, it doesn't matter which order they go in.

There may be some other non-electrical reasons for preferring one over the other in specific circumstances.

For instance, if you connect the LED directly to the PSU +ve, then accidentally shorting the LED to ground, as you might do with an untidy breadboard, will kill the LED. Resistor to PSU will be safer. This situation is asymmetric because shorts to ground are more common than shorts to PSU live when you're clowning around on a breadboard. This may be significant in your lab instructions.

There are other situations where multiplexing LEDs, or running them at various currents, is made easier by one or the other connection. This is asymmetric because of the popularity of low side switches, things like ULN280x and their ilk, which people tend to use for driving LEDs.