Hi Bomberomusician,
Welcome to the forums

BIAB defaults to a chord on beat 1 of bar one. That will always be there but, as you have discovered, it need not be heard.
There are a number of ways to make a single bar of silence precede the song. Here are a couple.
1. Right-click on bar 1 and then select
Bar Settings. Under
Instrument Changes Volume, select
ALL Instr and from the drop-down menu choose
Mute. Now go to bar 2, repeat the process and set the
ALL Instr volume to
Normal.
2. Right-click on bar 1 and select
Chord Settings. Now click on the drop-down menu on the right and select
Rest Only and make sure that
All Instruments is selected. Hit OK. You'll now find that your chord symbol has a single dot after it.
Hope this helps.
Can I ask, why are you after a bar of silence? The listener will be none the wiser if the first bar is silent or not.
All the best,
Noel