You can archive shipments in 3 ways:

1. Wait 24 hours, assuming the shipment is complete, after 24 hours the shipment will automatically be archived, to help keep things organised. 

2. Select the 'archive' option from the dropdown menu at the end of each shipment row in the shipments list

3. If you'd like to archive multiple shipments, you can select the tick boxes on the right hand side of each row and at the bottom of the page from the drop down menu select 'archive' . This will archive all the selected shipments.

Note : You can still search for archived shipments just like you can with non archived shipments

You can read all the statuses here