Archives are found in Communications.
You may wish to clear your Inbox and Sent box a little but still need to ensure that you have kept all records of your correspondence. Archiving is the tool for you to use, the items will stay in there but can be moved back if need be.
To Archive all you need to do is go to the email you wish to Archive, to the right you will find a little cog and click on the down arrow, here you will see choices you can make.
Click on Archive and the email will move straight to Archives.If you need to move the email back, again go to the little cog to the right click on the down arrow and select the action you wish to take.
This will move the email back to where it came from.