where is airplay on my macbook

See the following from How to AirPlay audio - Apple Support

To stream audio from your Mac to your Apple TV, HomePod, or AirPlay-compatible speaker:

1. Make sure that your Mac and speaker are on the same Wi-Fi or ethernet network.
2. Go to Apple () menu > System Preferences > Sound.
3. Under Output, select a speaker that you want to stream audio to. If you select Show volume in menu bar, then you can quickly change the audio output by clicking  in the menu bar.

You can't AirPlay to multiple speakers from the menu bar on a Mac.

Learn more about the requirements for using AirPlay and which speakers are supported.

and also the following from: How to AirPlay video and mirror your device's screen - Apple Support

AirPlay video from your Mac

1. Connect your Mac to the same Wi-Fi network as your Apple TV or AirPlay 2-compatible smart TV. 
2. On your Mac, open the app or website that you want to stream video from.
3. In the video playback controls, click .
4. Select your Apple TV or smart TV. Need help?

To stop streaming video, click  in the video playback controls, then choose Turn Off AirPlay.