How to enable autocomplete ?

There are specialized extensions for each file type, so you can look specifically for them. There are also some (I use one for Emmet Abbreviations) that cover several file types. It is also possible to have multiple that target the same file types as long as they are not in conflict, so you could use an autocomplete, a linter, and a style enforcer together on a TypeScript document, for example.

In VSC that feature is called "IntelliSense." The documentation for that feature can be found here: https://code.visualstudio.com/docs/editor/intellisense You will either have to save a file with an extension that VSC has associated with that language, or you will have to select which language to use in the bottom-right corner of the VSC editor, next to the notification bell, and the feedback button.