Microsoft offers Visual Studio Code for Linux as a .deb, .rpm, or .tar.gz file. From the following address:

choose and download (free of charge) the version that is suitable for your Linux distribution. When the download is complete, run the corresponding installer.

Notice: Alternatively, instead of downloading Visual Studio Code from Microsoft, you could try downloading it from your Linux Software Center (such as Ubuntu App Center, GNOME Software, etc.). However, PHP developers should download Visual Studio Code directly from Microsoft, as I have noticed some issues with the version available on the Ubuntu App Center

When the installation process is complete, launch Visual Studio Code.