When viewing a list of files in Retrieva you can order the list by any of the fields by clicking on the column header.

Clicking a column header once orders the list by that column in ascending order. Clicking again orders by the same column in descending order.

The header of the column that the list is ordered by is highlighted blue. There is an arrow next to the column title pointing downwards if the list is sorted in ascending order and upwards if the list is sorted in descending order.

The list defaults to being sorted by filename in ascending order.