I got the 6.5, and I don't know if it's the same.
but if you wanne add video+audio you have to select a video channel (V1) and an audio channel (A1).
then insert to timeline, and they will each appear in the timeline.
so:
1. windows > workspace > Single-track editing
2. load a clip in source screen
3. select in and output
4. go to the second screen
5. make sure you didn't disabled audio or video in the left screen below
6. select target V1orV2 and A1orA2orA3 in the right screen
and then click insert (below the left screen)
you can also just do it like overlay , its next to insert, but I like it the hard and controlled way
I hope I helped, otherwise I wasted my time bigtime cause I normally need to study :d