Begin by logging into your Omnisend account. Navigate to the section where reports or data exports are handled. Use Omnisend's export functionality to download the desired data in a standard format, such as CSV or Excel. Make sure to choose an appropriate timeframe and the necessary data fields for export. Once the export is initiated, download the file to your local machine.

Open the exported file and ensure that the data is clean and formatted correctly for import into Snowflake. Check for any inconsistencies, missing values, or special characters that could cause issues during import. Make sure the file is saved in a supported format, such as CSV. If necessary, use a spreadsheet application to clean up the data.

Access your Snowflake account and log in to the web interface. Verify that you have the necessary permissions to create warehouses, databases, and tables. If not, contact your Snowflake administrator to gain appropriate access.

In the Snowflake web interface, execute SQL commands to create a new database and the corresponding table(s) that will store the Omnisend data. Ensure that the table schema matches the structure of the data in your export file. For example, if your CSV has columns for `email`, `name`, and `signup_date`, your table should have corresponding columns with the appropriate data types.

```sql
CREATE DATABASE omnisend_data;
USE DATABASE omnisend_data;
CREATE TABLE omnisend_contacts (
email STRING,
name STRING,
signup_date DATE
);
```

Use Snowflake's web interface or a command-line tool like SnowSQL to upload the CSV file to a Snowflake stage. A stage is a temporary storage location within Snowflake. You can create a user stage or use an internal stage specific to the database or table. Use the `PUT` command if you're using SnowSQL.

```shell
PUT file:///path/to/your/file.csv @%omnisend_contacts;
```

After the file is staged, use the `COPY INTO` command to load the data from the stage into your Snowflake table. This command should match the columns in your CSV file to the columns in the Snowflake table.

```sql
COPY INTO omnisend_contacts
FROM @%omnisend_contacts/file.csv
FILE_FORMAT = (TYPE = 'CSV' FIELD_OPTIONALLY_ENCLOSED_BY='"' SKIP_HEADER=1);
```

Review the output for any errors and ensure that the data is loaded correctly.

Once the import is complete, run a few SQL queries to verify that the data in Snowflake is accurate and complete. Check for the correct number of rows and ensure that the data types and values match the source data from Omnisend. If any discrepancies are found, investigate and re-import if necessary.

```sql
SELECT COUNT(*) FROM omnisend_contacts;
SELECT * FROM omnisend_contacts LIMIT 10;
```

By following these steps, you can successfully transfer data from Omnisend to Snowflake without relying on third-party connectors or integrations.