How to Set Up Claude Code

Open your terminal and run:

npm install -g @anthropic-ai/claude-code

This installs Claude Code globally so you can run it from any directory. The installation takes about 30 seconds.

Verify the installation:

claude --version

Claude Code needs an Anthropic API key to work. If you do not have one yet, go to console.anthropic.com and create one.

Set the environment variable in your shell profile:

# Add to ~/.zshrc or ~/.bashrc
export ANTHROPIC_API_KEY="sk-ant-your-key-here"

# Then reload your shell
source ~/.zshrc

Alternatively, Claude Code will prompt you for the key on first run if it is not set.

Navigate to a project folder and start Claude Code:

cd ~/projects/my-app
claude

Claude Code launches an interactive terminal session. You will see a prompt where you can type natural language instructions. Try something simple:

> What files are in this project and what do they do?

Claude reads your project structure and gives you a summary. It has full access to read files, run commands, and make changes — but always asks for your approval before modifying anything.

The Claude Code interface is text-based. Here is what you need to know:

• Type naturally — describe what you want in plain English. No special syntax required.
• File diffs — when Claude wants to edit a file, it shows you the exact diff. You approve or reject each change.
• Tool usage — Claude can read files, search codebases, run terminal commands, and write files. It tells you what it is doing at each step.
• Approval flow — by default, Claude asks before making changes. You can adjust permission levels if you want it to be more autonomous.

This is the most important step for getting great results. Create a CLAUDE.md file in your project root. Claude reads this at the start of every session.

# CLAUDE.md

## Project Overview
This is a Next.js 15 app with TypeScript, Tailwind CSS, and Supabase.

## Tech Stack
- Next.js 15 (App Router)
- TypeScript (strict mode)
- Tailwind CSS for styling
- Supabase for database and auth
- Vercel for deployment

## Conventions
- Use server components by default
- Only add 'use client' when you need interactivity
- Use absolute imports from @/ prefix
- All API routes go in app/api/
- Database queries go through lib/db.ts

## Common Commands
- npm run dev — start dev server
- npm run build — production build
- npm test — run tests
- npx supabase db push — push migrations

## Known Quirks
- The auth middleware is in middleware.ts at the root
- We use a custom useUser hook, not Supabase's built-in one
- Image uploads go to Supabase Storage, not the filesystem

This is where Claude Code shines. Ask it to make a change that touches multiple files:

> Add a /api/users endpoint that returns a list of users
from the database. Include the route handler, a TypeScript
type for the response, and update the frontend to fetch
and display the users in a table component.

Claude Code will:

1. Read your existing code to understand patterns
2. Plan which files to create or modify
3. Show you the diff for each file
4. Wait for your approval before applying changes

This is fundamentally different from copy-pasting code from a chatbot. Claude Code sees your entire project and writes code that fits in.

Claude Code is git-native. Every change it makes is tracked by git, which means you can always undo. Here are common git workflows:

> Create a commit with a good message for the changes we just made

> Review the diff of my staged changes and suggest improvements

> Create a new branch called feat/user-profiles and move our changes there

You can also ask Claude Code to create pull request descriptions, review code, or resolve merge conflicts. It reads the git history and understands your branch structure.

You are ready. Here is a real-world prompt to test Claude Code's capabilities:

> I want to add a blog system to this project. It should:
- Use MDX files in a /content/blog directory
- Generate static pages at /blog/[slug]
- Include a blog index page with cards for each post
- Support frontmatter for title, date, description, and tags
- Have good SEO with meta tags and JSON-LD

Read the codebase first to understand our patterns,
then implement this step by step.

Claude Code will explore your project, build a plan, and implement it file by file with your approval at each step.