Begin by exporting the data you need from Webflow. Log into your Webflow account, navigate to the CMS Collection you want to export, and click the "Export" button. This will download the data as a CSV file, which is a commonly used format for data transfer.

Open the exported CSV file using a spreadsheet application like Microsoft Excel or Google Sheets. Review the data for completeness and accuracy. Clean the data by removing any unnecessary columns, correcting any errors, and ensuring consistency in data formatting.

If you haven't set up a PostgreSQL database yet, install PostgreSQL on your system or use a remote PostgreSQL server. Create a new database using the `CREATE DATABASE` SQL command. Ensure that you have the necessary permissions to create tables and insert data into this database.

Based on your CSV file, design the table structure in PostgreSQL. Define the columns and their data types using the `CREATE TABLE` SQL command. Ensure that the structure aligns with the data contained in your CSV file, including constraints such as primary keys and foreign keys if needed.

Use a script or a tool to convert the cleaned and reviewed CSV data into SQL insert statements. You can write a simple Python or Bash script to parse the CSV file and generate the corresponding `INSERT INTO` SQL commands. This step prepares the data for insertion into the PostgreSQL table.

Execute the SQL insert statements on your PostgreSQL database. You can use the `psql` command-line tool to run these statements. If using psql, you can feed the SQL file containing insert statements using `\i yourfile.sql`. Make sure that all data is inserted correctly.

After inserting the data, run queries on your PostgreSQL database to verify that the data has been transferred accurately and completely. Check for record count consistency and spot-check some data values to ensure they match the original data from Webflow. Make any necessary adjustments if discrepancies are found.