open-source-silicon.dev

You can use a measure statement like this to find the average current:
.meas tran iavg_dig AVG i(Vddd)

And then multiply the average current by the voltage? Is this the correct way to obtain the average power? I remembered that perhaps an integration was needed, but I'm not sure...

Yes, exactly. The above command performs the integration for the current numerically.

Average power = average(v(t)*i(t)). If the voltage is constant, you can pull it out of this expression. So average power is just average current times that constant voltage.

Average means integrating over time and dividing by the integration time. That's what the  meas command does for you.