If you want to import listings the easiest way is using some WordPress import plugins, for example https://wordpress.org/plugins/wp-all-import/ You can map imported data to listing fields, depending on what attributes you added. For example if you added an attribute named “price” then it’s stored as a post meta field with “hp_price” key, listings itself are custom posts with “hp_listing” type.
So you can just import items with “hp_listing” type and map data to attributes that you added for listings (depending on how you named them). I understand that it’s a bit confusing, I plan to release an import/export extension for HivePress.