The export button (to the right?) will allow you to export the search results of the entered query to a CSV file. To export the items, click the "Export" button.
There are two options to select the items you want to export to a CSV. Either you export all results from a search query, or you select a subset of items from the search results.
To select a subset of the search results, click "Selective Export" in the Export menu.
After making a selection, click the 'CSV' button. The amount of items that will be exported is indicated in the bubble next to 'CSV'.
The amount of items you can export is limited, but authenticating will increase this limit.