By default, Spectre does not save currents. To save a specific current:
1. Go to Outputs -> To be plotted -> Select on design. Then select required currents on a schematic.
2. Go to Outputs -> Save all.. -> Select device currents (currents) -> choose selected.
3. In your case it's also useful to go to Outputs -> Save all.. -> Select power signals to output(pwr) -> select "all".
If it is a static power, you can simply select power in DC operating point annotation for your resistor (if you only want to measure power dissipated there). Otherwise, probe the current and voltage into calculator and calculate the power yourself.
Hopefully, that helps.