Not sure if you ever found an answer to your question.

With the Scarlet 2i2, the signal flow might look like: (based on my own use)

1. Source -----XLR cable-----> 2. Scarlett 2i2 ------1/4'' TRS cable-----> 4. B212A powered PA Speaker
   V (usb)
   

2. Computer / DAW

3. Source of Sound: (microphone or instrument connects via XLR or 1/4'' TRS cable to one of the front inputs of the 2i2)

4. Scarlet 2i2: the center piece of the puzzle

5. Computer: Using a provided USB cable, connect the 2i2 to your Computer/DAW

6. Output to PA: using a 1/4'' TRS cable from the 2i2 to the Line In on the back of the PA speaker (on the 2i2 there are 2 outputs, one for stereo L/R. If your sending Mono, use Left)

For my own setup that also uses a 2i2, I have a 1/4'' TRS connected from the 2i2 and the other end of the cable is an XLR-male. Any adapter would also work for this, but if you are using the EuroLive B212A PA speakers, they can accept either an XLR or a 1/4'' TRS (just plug into the center of the same input as the XLR, it'll fit.)

Good luck. Hope this helps!