Spectrum Analyzer Connection.

Hi.

not sure if this is the correct forum to post this, but I'm sure a moderator can move it if required.

I have a Scarlett 2i2 audio interface connected to my MacBook Pro, in order to use my mic in Logic.

My aim is to have speakers and headphones as optional outputs, and to be able to see the spectrum analyser irrelevant of which output I choose.

The fungeneration RTA-31 looks ideal, but I'm totally confused as to how to connect it, so it works with both headphones or monitor speakers.

I obviously know how to connect my monitor speakers and headphones to the 2i2, but am totally perplexed as to how to introduce the RTA-31 to the combination.

I simply need to know what connects to what, and where, in newbie language.

If anyone can provide step by step instructions, I would be extremely grateful.

Thank you all in advance.