If you want to import content from any source, you first need to click on either of the Install Now links that are under the available platforms (visible in the preceding screenshot). WordPress uses additional plugins to handle the importing, and it first needs to install them to carry out the procedure.
Importing content from each of the available platforms is a bit different, but the general process looks similar, so we're going to use another WordPress site as an example here—that is, we're going to import content from another WordPress website. For that to work, all we need to do is click on the Install Now link that's within the WordPress section (it's the last one in the preceding screenshot), and then, when the installation completes, click on the new Run Importer link that will have just appeared. Refer to the following screenshot:
This will take you straight to the importer panel:
It is a very simple interface where all you have to do is take a WordPress export file and upload it to your site. The platform will take care of extracting the archive and importing the content into it. As a result, your site is going to be filled with new posts, pages, custom fields, navigation menus, and even comments.
The main purpose of this feature is to help everyone who's migrating their sites from platforms such as Blogger or LiveJournal. Imagine if someone had a Blogger blog with over a hundred posts in it. Going through each one individually and inputting it in to WordPress by hand would be too time-consuming. With this feature, it can be done in under a minute.