Question abou tplaying 2 tracks at once

I am starting to play a little bit with rosegarden an recording tracks.

I've figured out how to record tracks.

I recorded a track, and then to record the second one, I press record,
and I can get the first track to play while recording the second.


Well, when I want to listen to the recorded tracks together, I can not
get this to work:(

I can only hear one of the other.


How can I get both tracks to play at once?

Thanks

Joseph