Begin by logging into your Vitally account. Navigate to the data or reports section where you can export data. Use the export functionality to download the required dataset as a CSV file, which is a common format for data transfer.

Ensure that you have DuckDB installed on your system. You can install DuckDB via package managers like `pip` for Python users or download binaries from the DuckDB website. Ensure your environment is ready to execute SQL queries.

Open the exported CSV file in a spreadsheet application or a text editor. Examine the data for any inconsistencies, missing values, or formatting issues that might cause errors during the import process. Clean the data to ensure it is in a consistent format and ready for import.

Launch DuckDB by opening a terminal and typing `duckdb` to start the DuckDB shell. Create a new database for your project by executing the command:
```
CREATE DATABASE vitally_data;
```

Within the DuckDB shell, create a table that matches the structure of your CSV file. You must define the table schema, including column names and data types, to match those of your CSV file. For example:
```sql
CREATE TABLE customer_data (
customer_id INTEGER,
name VARCHAR,
email VARCHAR,
signup_date DATE
);
```

Use the `COPY` command in DuckDB to load data from your CSV file into the newly created table. Ensure that the path to your CSV file is correctly specified. For example:
```sql
COPY customer_data FROM 'path/to/your/file.csv' (DELIMITER ',', HEADER);
```
This command reads the CSV file and inserts the data into the `customer_data` table in your DuckDB database.

After loading the data, run a few queries to ensure that the data has been imported correctly. For instance, you can use a simple `SELECT` statement to check the first few rows:
```sql
SELECT * FROM customer_data LIMIT 10;
```
Review the output to ensure that the data matches the original CSV file. Perform additional queries as needed to validate the integrity and completeness of the imported data.

By following these steps, you can manually transfer data from Vitally to DuckDB without relying on third-party connectors or integrations.