We’re working on making Gemini 3 available to all Firebase Studio users as soon as we can! 
In the meantime, if you’re eager to try it out, you have two options:
In Code Mode (</>):
You can input your personal Gemini API key under “AI Settings” in the Gemini pane. From there, simply select your preferred model.
Note: This won’t update the model used in Prototyper Mode.
Via the CLI:
If you’re a Google AI Ultra subscriber and comfortable with the command line, open the Command Palette (Cmd+Shift+P on Mac or Ctrl+Shift+P on Windows/Linux) and select “Terminal: Create New Terminal.” Then, simply type gemini to launch the Gemini CLI. Details on the roll-out of Gemini 3 in Gemini CLI are here