Select the Data Object and CSV file

Step 2: Select the Data Object and CSV file.

Choose an object. For example, select the Account object. If object name does not display in the default
list, check "Show all Salesforce objects" to see a complete list of objects that we can access.

Click "Browse" button, to select the source CSV file from the computer for updating records into
salesforce.

Click on "Next" Button

Above Mentioned, the Step 1, Step 2 in the update operation which is similar to Insert Operation
Note: The CSV file should be like the following screenshot

Step:2a Choose fields to use for mapping
Here the select the field(External Id field) for matching on Account



Upsert uses an indexed custom field or external ID to determine whether to create a new record or
update an existing record.
-- If the external ID is not matched, then a new record is created.
-- If the external ID is not matched once, then the existing record is updated.
-- If the external ID is not matched multiple times, then an error is reported.
External ID:External ID is a flag that can be added to a custom field to indicate that it should be indexed and treated
as an ID.
It is available on all objects that support custom fields.
An Object can have three(3) External ID fields for the following data types:
-- Text
-- Number
-- Email
Click on "Next" Button