Start by logging into your PayPal developer account. Navigate to the “My Apps & Credentials”� section to create a REST API app. This will provide you with client credentials (Client ID and Secret) necessary for accessing the PayPal API. Use these credentials to request an access token from the PayPal OAuth2 API endpoint, which will authorize you to retrieve transaction data.

Utilize the access token obtained in the previous step to make a GET request to the PayPal Transactions API. Specify the desired date range and transaction types in your request to filter the data you need. The response will include transaction details in a JSON format, which you can parse to extract relevant information like transaction ID, amount, date, and payer details.

Once you have the transaction data, clean and structure it into a tabular format suitable for DuckDB. Convert the JSON data into a CSV format or create a structured data frame using programming languages like Python or R. Ensure that the data types for each column match your intended DuckDB schema, such as ensuring date fields are in the correct format.

If you haven’t installed DuckDB yet, download and install it from the official DuckDB website (duckdb.org). DuckDB is available for multiple platforms and can be installed using package managers like pip for Python (`pip install duckdb`) or via binary downloads for other languages and environments.

Open your DuckDB environment and create a new database file. Within this database, define a table schema that matches the structure of your prepared transaction data. Use SQL commands like `CREATE TABLE` to specify column names, data types, and any constraints you wish to apply.

Import your prepared data into the DuckDB table. If you have saved your transaction data as a CSV file, you can use the `COPY` command in DuckDB to load the data directly:
```sql
COPY your_table_name FROM 'path/to/your_data.csv' (AUTO_DETECT TRUE);
```
Alternatively, if you are using a programming language, you can leverage DuckDB's API to execute SQL commands that insert your structured data frame into the table.

Once the data is loaded, run queries to verify that the data has been inserted correctly. Use basic SQL queries to check data integrity, such as counting rows, checking for null values, and ensuring data types are correct. With your data now in DuckDB, you can perform complex queries and analysis as needed.

By following these steps, you can successfully move PayPal transaction data into DuckDB without relying on third-party services, thus maintaining greater control over your data processing workflow.