afaik the "compiling from source code" page still suggest to change build_envs in platformIO.ini. This is not necessary any more when using VSCode.
- click on the small "folder" icon
- type part of the name you need, then you'll see a drop-down so select from it
- click on the checkmark icon for compiling
- click on the "plug" to start serial monitor
- click on "left arrow" for uploading firmware to your board

