Update First Run tutorial

[melissawm]

Description

Adds a link to the notebook guide, reviews some wording and adds a code snippet for completeness. Also removes mention to the preflight document for now until a decision is made about where to fit it.

Tests

Documentation builds correctly locally.

Checklist

Before submitting this PR, please make sure (put X in square brackets):

• [N/A] I have performed a self-review of my code. For an optional AI review, add the gemini-review label.
• [N/A] I have necessary comments in my code, particularly in hard-to-understand areas.
• [N/A] I have run end-to-end tests tests and provided workload links above if applicable.
• I have made or will make corresponding changes to the doc if needed, including adding new documentation pages to the relevant Table of Contents (toctree directive) as explained in our documentation.