Feature: Mass data can be imported into Salesforce via files in CSV format.
Instructions: Setup -> Data Management -> Data Import Wizard
Launch the Wizard
1. Select the objects you want to import, i.e. Contacts.
2. If adding new data, select the unique identifying fields that Salesforce will try to match to avoid duplication. If updating existing data, select the unique identifying field to update the record.
3. Attach the CSV file. The file will be formatted with headers on the top row to identify the data in the columns below.
4. Match the Salesforce object fields with the CSV headers. A sample of the data will be shown.
5. The data will be imported.