Converting mono to sterio

I followed the direction in u-tube but could not make it stereo. I copied a single track to dual track and then it will not give me the option of combining the tracks.
I am trying to make a home recorded audio which was mistakenly recorded in one track. I tried to convert that in sterio without luck.
Any help will be appreciated.

You can convert your existing recording by using the Track Control Panel Audio Track Dropdown Menu - Audacity Manual. Just select Spilt Stereo to Mono and delete the empty track. The resulting mono file should play as stereo. If you need two tracks, Ctrl-A, Ctrl-D to duplicate the mono track, then on the dropdown menu on the upper track, select Make Stereo Track.