The first step is a half box which the lady will do while the man will perform the entire waltz box. She will be mirroring the man's steps who steps his left forward first, now lady's move your right foot back. Then he goes backward while she goes forward and then both to the side again to find their original box. If we trace their steps will see the invisible waltz box made with their feet, for the underarm step in waltz the lady will perform only half of the box while the man continue to do the full waltz box.
The second step belongs also to the lady's and it's the second half of the box, while he will still do the waltz box she will perform the underarm turn. The lady walks under the man's arm for six counts while he is dancing the box. Both partners should count the beats so they know they are in time, and the lady will only perform the underarm turn.
The third step is finishing the box. Now that the lady has finished her underarm turn it's time to continue the invisible waltz box, this the step you will finishing the waltz with.
In other words the easy steps for the man are: left- side- together- underarm turn- left- side- together- right- side- together and now for the lady: right- side- together- left- walk- walk- walk- side- together- left- side- together.
Remember that the lady mirrors the man's steps and gentleman make sure you lead this step when stepping back on your right.
The count is still 3/4 so count it: one- two- three and Man: left- side- together- underarm turn- left- side- together- right- side- together and the lady: right- side- together- left- walk- walk- walk- side- together- left- side- together. Enjoy this nice video.