The Model from Picks button in the Model Window is only active if fits to observations have been made from the Fit Window. When chosen, the line fits made to individual reflectors are used to determine the depth of the reflector and the RMS velocity of all the material above the reflector using the Dix equation. These values are shown for the best fit lines when the Fit Statistics button is pressed. Once the Model from Picks button is pressed in the Model Window, the velocity model in the Model Window will be updated with the estimated interval velocities. You can then choose to generate the arrival times consistent with this new model by clicking on the Update Times and Plots button in the Model Window.