Beaver Builder uses the native WordPress import feature to allow easy import and export of its templates.
To start with Go to Tools > Import in the WP admin. In the WordPress section at the bottom and click on Run Importer. It imports posts, pages, comments, custom fields, categories and tags from a WP export file.
You will get an option on the next page to choose an XML file of the template which you want to import. After choosing the desired XML file, click on Upload File and Import button (as shown in the screenshot below).
After this, you will receive a confirmation message. Now, you can use this template in the Page Builder. You can Check this article for using the template on the front end.
If you have your custom templates and imported templates then it’s a good idea to organize them efficiently. You can do that by enabling Template admin interface from Beaver Builder settings.
Go to Settings > Page Builder. Under Template Settings check Enable Templates Admin and Save settings.
This will allow you to manage and categorize your templates just like you do for Posts.