Google Docs Formatting – How to Change Default Indent and Set Your Own

See

• .NET Documents List Uploader
• Google Support Link

As noted by Felipe Alvarez, this is no longer available as an option. Therefore, while this answer was correct two years ago when the product was Google Docs, it no longer applies to the current Google Drive app.

Assuming you mean opening documents from your list, that's in the Google Docs settings on the "General" tab.

Where items open:

Your choices are:

• In a new window
• In the current window

Screen shot:

Select the latter for what you want.