1. Sign Up and Create a Project: Head over to the Supabase website and either sign up for a new account or log in if you already have one. Create a new project by filling in the necessary details like project name, password, and the database region.
2. Get API Keys: After your project is set up, go to the settings page and find the API tab. Here, you'll see your API URL and anon key. You'll need these to connect your Svelte app to Supabase.

1. Install Svelte: If you haven't installed Svelte yet, you can set it up by running:
   ```bash
   npx degit sveltejs/template svelte-supabase-app
   cd svelte-supabase-app
   npm install
   ```

1. Install Supabase: In your Svelte project directory, install the Supabase JavaScript client with:
   ```bash
   npm install @supabase/supabase-js
   ```

1. Create a Supabase Client: In your Svelte project, create a new file src/lib/supabase.js and set up your Supabase client:
   ```javascript
   import { createClient } from '@supabase/supabase-js';

   const supabaseUrl = 'YOUR_SUPABASE_URL';
   const supabaseAnonKey = 'YOUR_SUPABASE_ANON_KEY';

   export const supabase = createClient(supabaseUrl, supabaseAnonKey);
   ```

   Replace YOUR_SUPABASE_URL and YOUR_SUPABASE_ANON_KEY with the values you got from your Supabase project.

1. Fetch and Display Data: Open a Svelte component, like src/routes/index.svelte, and add the following code to fetch and display data from Supabase:
   ```svelte

   Supabase Data

   {#each data as item}
   • {item.column}
   {/each}
   \`\`\`

1. Create a Form to Add Data: Modify your Svelte component to include a form for adding new data:
   ```svelte
   Add Item

   Supabase Data

   {#each data as item}
   • {item.column}
   {/each}
   \`\`\`

1. Enable Row Level Security (RLS): In the Supabase dashboard, go to your table settings and enable Row Level Security (RLS).
2. Define Policies: Create policies that define who can access and modify data. Use SQL policies like:
   ```sql
   CREATE POLICY "select_your_table_name" ON "public"."your_table_name"
   FOR SELECT
   USING (
   authenticated()
   );
   ```
3. Testing: Make sure the policies work as expected by testing the behavior in different scenarios (authenticated vs. non-authenticated users).

1. Build Your Application: Run the build command to compile your Svelte project:
   ```bash
   npm run build
   ```
2. Deploy: Deploy the compiled application to your preferred hosting provider. Services like Vercel, Netlify, or even traditional servers support Svelte applications.

This guide outlines a basic flow to set up Supabase with Svelte. For more advanced features, refer to the respective official documentation of Supabase and Svelte.