To measure voltage in Multisim we use probes.
1. Locate the voltage probe icon at the left hand side of the screen
2. Place this on a wire in your circuit.
3. Locate a reference probe on the left hand side of the screen
4. Place this on the wire that you would like to measure with reference to. Here we are measuring the voltage across R1.
5. Select the voltage probe
6. Change the voltage reference to REF1.
7. Run the simulation
8. The voltage across the resistor should now show.