How to install Vision OS simulator

Go to Apple's download beta page for XCode 15 beta
Download any beta version of your choice
Here's the link for the latest beta 8
Unzip it
Move it to Applications by simply dragging it.
Make the beta version the default XCode

sh

sudo xcode-select -s /Applications/Xcode-beta.app

Run first launch

sh

xcodebuild -runFirstLaunch

There will be an option to download the simulator on the first launch.
If you want to download it manually, you can use this link

Install the simulator manually

sh

xcrun simctl runtime add ~/Downloads/visionOS_1_beta_3_Simulator_Runtime.dmg