Begin by accessing your Klaviyo account and navigating to the "Lists & Segments" section. Select the list or segment you wish to export. Use the "Export List to CSV" option to download your data as a CSV file. Ensure you have the necessary permissions to export data.

Open the exported CSV file using a spreadsheet application like Microsoft Excel or Google Sheets. Review the data to ensure it is accurate and consistent. Make any necessary adjustments such as cleaning up headers, removing duplicates, or standardizing formats to match the schema in Teradata.

Log into your Teradata Vantage account. Ensure you have the appropriate permissions to create tables and upload data. If you do not have access, contact your database administrator.

Using the Teradata SQL interface, write a SQL script to create a table that matches the structure of your CSV data. Define each column with the appropriate data type and constraints. For example:
```sql
CREATE TABLE KlaviyoData (
CustomerID INTEGER,
Email VARCHAR(100),
SignupDate DATE,
... // Add columns as per your data structure
);
```

Transfer the CSV file to a location accessible by your Teradata environment. This could be a local machine connected to the Teradata server or a directory within the server itself. Use secure methods such as SCP or SFTP to ensure the data is transferred safely.

Utilize Teradata's native tools like BTEQ or Teradata's SQL Assistant to load the CSV data into the newly created table. Use the following general approach:
```sql
.LOGON your_teradata_server/username,password;
.IMPORT DATA FILE = 'path_to_your_csv_file';
USING (CustomerID INTEGER, Email VARCHAR(100), SignupDate DATE, ...)
INSERT INTO KlaviyoData (CustomerID, Email, SignupDate, ...);
.LOGOFF;
```
Make sure the column names and data types in the USING clause match those in your table.

After loading the data, perform data validation checks to ensure accuracy and completeness. Run SQL queries to count records, check for null values, or compare sample data against the original CSV. Address any discrepancies by adjusting the data load process or cleaning the source data.

By following these steps, you can effectively transfer your data from Klaviyo to Teradata Vantage without relying on third-party connectors or integrations.