Begin by familiarizing yourself with the data structure in Zendesk Sell. Identify the data you need to move, such as leads, contacts, deals, or custom fields. Use Zendesk Sell's API documentation to understand how this data is organized and how to access it via their API.

Log into your AWS Management Console and navigate to DynamoDB. Create tables in DynamoDB that will correspond to the data you plan to migrate from Zendesk Sell. Define the primary key for each table, and set up any necessary attributes and indexes to accommodate the data structure.

Write a script in a programming language of your choice (e.g., Python, JavaScript) to interact with the Zendesk Sell API. Use API endpoints to authenticate and retrieve the data you need. Implement pagination handling if your data exceeds the API limits for a single request.

With the extracted data, transform it to match the schema you defined in your DynamoDB tables. This might involve renaming fields, changing data types, or flattening nested structures. Ensure that the data transformation aligns with DynamoDB's requirements, such as attribute names and types.

Develop a script that uses AWS SDKs to insert the transformed data into DynamoDB. Ensure your script correctly maps the transformed data to the corresponding DynamoDB attributes and handles batch writing to optimize performance.

Run your scripts in a test environment to ensure the data is being correctly extracted from Zendesk Sell, transformed, and inserted into DynamoDB. Check for data integrity, and validate that all fields are correctly populated. Make necessary adjustments to your scripts to address any issues.

Once testing is successful, execute the migration process in your production environment. Continuously monitor the process to ensure data is correctly moved and that no errors occur. After completion, verify the integrity of the data in DynamoDB by comparing samples against the original data in Zendesk Sell.