Hi, i'm trying to get voltage gain by using the oscilloscope but i couldn't get the right value. I tried watching youtube to check where I was wrond but i still couldn't figure it out. Where am I supposed to put Channel A and Channel B of the oscilloscope to get the right voltage gain?

 

The input is 6V peak so the scope channel A which is set to 5V per division produces a sinewave amplitude a little more than 2 divisions peak-to-peak as shown.
The gain will be less than (2.7k//1.2k)/1.2k= 0.9 times but the channel B is set to show 500V per division and the output of less than 16V peak-to-peak is shown correctly as almost nothing.

The 0.0082uF capacitor value is very low to pass 10Hz into 1M ohms so it causes a additional voltage loss.

 

As AG noted, that circuit is configured for a gain of less than one.
What gain were you expecting?

 

Since the 'scope was set to show an output of 500V (!) per division then I guess he is using a miracle to obtains a voltage as high as 1000V or more to be shown.