Spotify won't play on speaker when I leave home

Do I need to download the Sonos App on my MacBook Air for the Sonos One Speaker for my wife to listen when I am away with my iPhone?

No. Asuming your wife has the Sonos app on her phone (if not, she needs to install it and select to connect to existing system): then she just needs to add her Spotify account to Sonos, as per the link given by Bruce.

In fact, even as things are now there is nothing I can see to prevent your wife using Spotify Connect to play on the Sonos One. Or she coukd use Airplay 2 to play music on the Sonos One.

Your phone is just a remote control for Sonos. Its absence should not impair in any way her ability to play music.

Sorry for my confusion. Wife has a separate(non Premium) Spotify account on her phone. The other Premium of mine is on the laptop. So instead of using her iPhone when I'm gone can she somehow use the laptop? If so, can we both then listen individually. Me at the gym on my phone and ear buds and her at home on the Sonos One?

Again I apologize for my ignorance but what is Spotify Connect and Airplay 2 and where are they?

The only way a free Spotify account can be used is for your wife to use the Spotify app on her phone and cast the sound to the speaker using Airplay, if her phone is an iPhone.

You cannot use a single Spotify Premium account to play in two different places simultaneously.

When you play Spotify on Sonos using your phone do you do so using the Sonos app or the Spotify app?

It sounds like your best bet would be a Spotify Family account.

Again I apologize for my ignorance but what is Spotify Connect and Airplay 2 and where are they?
Spotify Connect allows you to play music on Sonos from the Spotify app. Airplay is a method for sending audio from an Apple device to a speaker.

And there are several ways of getting to send an AirPlay 2 signal, which depend on the Apple device you're using. On newer iPhones, you pull down from the top right corner, and it's the box in the top right of that resulting page. Click on the circles with a diamond pointing up in the top right of that box (I sense a theme here, top right, all the way...), and you get to the selection screen for AirPlay 2. It will show you all available AirPlay 2 speakers, including your Sonos, assuming that they're AirPlay 2 capable.

The other way is to...cripes, I have no idea, I never use it. Here's the Apple webpage about it all.

https://support.apple.com/en-us/HT202809

Ah, it's a swipe up on older devices. For some reason I thought it was in settings.

I see what Spotify Connect is. Here is the part I don't understand.....when I am out of the house at the gym and I connect my ear buds to my phone and listen to Howlin Wolf and my wife is home and wants to listen to Adele. I tried using Spotify Connect on the laptop to play from the location on the device menu but when I left the house and tried to play what I wanted on the phone thru ear buds it didn't work....I heard what she was playing in the house. Am I making any sense? Or is this the reality of Spotify and Sonos speakers?