You can easily import data from external sources into Salesforce as long as the external source can provide you with a comma-separated values format (.csv).
Salesforce supports two main methods for importing data:
- Data Import Wizard: This is an in-browser wizard that is accessible through the Setup menu. It lets you import data in your account, contacts, leads, campaign members, solution-standard objects, and in custom objects. It's a very simple interface that lets you import up to 50,000 records at a time. It can detect and avoid duplicates while importing and it's also possible to deactivate all workflow rules while doing the import. The following screenshot shows the interface of the Data Import Wizard in Salesforce: