The 'Oscillator Offset' control allows you to steer out the offset between the oscillator in your sdr and 'true' time. The following example uses Thetis to observe the process. First start and connect Thetis. Then tune to the highest frequency WWV signal you can copy and set the 'Zoom' control to max:

Spin the 'Oscillator Offset' slider while observing the signal on Thetis. It will move left/right, center the signal:

At this point you can click the 'Save Configuration' button to store the result.