Salesforce's Data Loader is a free tool that allows you to bulk update Salesforce with data from CSV files.
1. Click on Setup.
2. Search for Data Loader in the search box on the left-hand side and then click Data Loader.
3. Download Data Loader for your appropriate version (Windows or Mac).
Recommended next reading:
How do I download Ebsta Sync's Data Report?
How do I bulk upload Ebsta Sync's up-to-date data into Salesforce?