When using the website, ensure you are logged in with your email address and password.
Once in your Inbox, open the conversation you want to remove from your inbox and then click the green ‘Archive’ button.
If you change your mind, you can find the conversation again by selecting the 'Archived' folder in your inbox menu. Then you just need to reopen the conversation and click the ‘Unarchive’ button.
When using the app, once logged in.
Click 'Inbox' along the bottom
Locate the messages that you would like to archive and hold down your finger on this. A message will then pop up asking if you 'no longer need this message?
Tap 'OK' and this will archive the message