Fairly simple.Once you sneak into the Bar via the crate,you will find yourself behind the counter.
Firstly grab the bottle of Chloroform from the bar,equip it in your inventory and then pour it into the ink well,which then proceeds to knock out Zane.
Next, activate the sign switch on bottom left,which will send Cue-ball away to fix the fuse
Lastly press the panic button on underside of bar,which reveals the false ice cream facade of the bar.Matches will then come over to the bar,looking for the panic switch to revert back to the bar again.As he does this a bottle will drop.Pick this up,equip the bottle and activate the panic switch once more.As matches leans over to flick it again,smack him over the head with the bottle
After a small cutscene the achievement will pop
while you are behind the counter,look to yor far right wher you will see 3 numbers,,7,23,30 which will help you get the Escape Artist achievement later in episode 2.
Also there is a piece of paper on top of bar.DO NOT look at this if you want to get the Door prize acievement