To place a task in the archive, right-click on it and use the Archive option at the top of the dropdown menu.
By default, this option is only available in the last column of your Kanban board. Should you wish to enable archives in any other column as well, go to Settings - Board Editor and use the pencil icon under a chosen column’s name, to set it to allow for tasks to be archived there.
And to file away all of the tasks in a column, either right-click on the header of that column or click on any space in that column, to select the Archive all option.
Using the archive is easy - to enter, click the + # archived tasks link at the top of your last column:
A list of all archived tasks for this particular column will be presented.
However, once you’re in this view, you can search through tasks archived on any boards, swimlanes, or columns. Also - you’re welcome to search the archive with the magnifier icon - it supports the same set of search queries, that a board’s Global Search does.
Want your tasks to get archived automatically? Take a look at how to set an auto-archive feature.