The WakaTime plugin is open-source on GitHub.
Press F1 or CMD + Shift + P and type install. Pick Extensions: Install Extension.
Type wakatime and hit enter.
Restart Visual Studio Code.
Enter your API key , then press enter.
(If you already have a WakaTime plugin installed, you won't be prompted for your api key.)
Use VS Code like you normally do and your coding activity will be displayed on your WakaTime Dashboard.