Orchestrate copilot for VScode is currently in Public Preview, so you need to install it manually using a .vsix file. Follow these steps to install the extension:
1

Download the installer

Click here to download the .vsix installer file.
2

Open VScode and the installer

Launch VScode and open the folder that contains the .vsix file.
3

Install the extension

Right-click the .vsix file and select Install Extension VSIX.