Creating Folders and adding presentations accordingly, will make it easier for you to organize and manage them. To create a folder, you'll find the "Add folder" button on the left sidebar of your homepage, below your Documents list.
You can also create your first folder by clicking on a presentation and then hitting the folder icon button. Name it and add a short description if you like.
You can edit or delete the folder by accessing it and clicking on its Settings button. Deleting it won't affect the documents contained in it, as they will still be accessible in your dashboard.
In order to add a presentation into a folder, find the deck among your documents, click on it and look for the folder icon. Click on it to see all your folders, then just select the one you'd like to send the document to.
To remove a presentation from a folder, access the folder and click on the presentation. Again, look for the folder icon, click on it and just deselect the folder in which the presentation is currently stored.