The import functionality is only available for admin users and Backend users for which the Page TSconfig option options.impexp.enableImportForNonAdminUser has been enabled.
Make sure that any required extensions are installed and the database scheme is up-to-date before starting the import. Otherwise the data related to non-existing tables will not be imported.
Go to the import module
In the page tree, right-click the page you want to import to (1) and select More options ... > Import (2).
Upload the export file
On the second tab of the import module you can upload the export file to your target TYPO3 instance.
Select the file to upload (1) and click the Upload files button (2).
Then switch to the Import tab (3).
Configure the import
On the first tab of the import module you can configure the import.
First select the uploaded export file (1). Then adjust the general settings (2). Finally, press the Preview button (3).
Checking Update records means that existing records with the same UID will be updated instead of newly inserted.
Checking Do not show differences in records prevents calculation of differences between existing and imported records. Note: The compare function is currently broken and therefore disabled in the screenshot.
Check the data to be imported
A tree with the records to be imported is displayed below the configuration form (1). If you change any of the options (2), you can reload this preview with the Preview button (3).
Perform the import
Click the Import button.