Folders allow you to organize your various messages in a way that makes sense to you, beyond the standard Inbox. To move a message (or messages) from the Inbox into a folder, you will want to select the checkbox for that message, and use the “Bulk Action” dropdown to select “Archive To Folder”. From there, you will have the option to select a pre-existing folder, or optionally you can create a new folder directly from this menu by selecting “Create Folder”, and entering your desired folder name, and clicking “Add”.
To manage existing folders, simply hover over the folder in the left-side menu. This will bring up two buttons, allowing you to rename or delete the folder. It is important to note that if you delete a folder that contains messages, those messages will be moved to your inbox after the folder is deleted.