To open the Option dialog, choose Options, Options ... from the menu bar  :
 
 

The following options are available : Insertion : when Single notes is selected, CTRL-clicking in a measure will create a single note. If Simultaneous notes is selected, simultaneous notes will be inserted If you check the "Automatically add rhythm", when inserting a note, a linked rhythm will be added. MIDI : select the MIDI device for playback (try until one works ...)

To open the Tablature Parameters dialog, choose Options, Tablature Parameters from the menu bar  :

The following options are available for the current tablature, they will be saved with it : MIDI : you can specify channel and programs for the playback of chords, guitar notes and bass notes. Default channels are 0,1 and 2 respectively. Default programs are Acoustic Grand Piano for chords, slap bass2 for Bass and IdontRemember for solo. Beats per minute : enter the BPM of your song.