A Timeline element can be added in the slide editor, hitting the Add Content Block. You'll get this interface in order to create and edit the timeline.
As shown, there's a bar button on top of the sequence, to add items to the timeline. You can also add an item using the + button on the options next to each item.
Each item can have an image and text, just hit each's block in order to edit it. Take advantage of Slidebean's gallery of images and icons, or upload your own ones. Finally, select the items distribution, to organize the display.
In order to remove or reorganize an item in the sequence, use the buttons displayed in the right-hand side of the item when you hover over it. To move it up or down, just drag it from the arrows.
Hit Done to save the changes when you've finished.