In the toolbar in the bottom right corner you will see a item that looks like the following:
After clicking on it you will get the option to indent using either spaces or tabs. After selecting your indent type you will then have the option to change how big an indent is. In the case of the example above, indentation is set to 4 space characters per indent. If tab is selected as your indentation character then you will see Tab Size instead of Spaces
If you want to have this apply to all files and not on an idividual file basis, override the Editor: Tab Size
and Editor: Insert Spaces
settings in either User Settings or Workspace Settings depending on your needs
Edit 1
To get to your user or workspace settings go to Preferences -> Settings. Verify that you are on the User or Workspace tab depending on your needs and use the search bar to locate the settings. You may also want to disable Editor: Detect Indentation
as this setting will override what you set for Editor: Insert Spaces
and Editor: Tab Size
when it is enabled
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