When creating visualizations in the visualization canvas, there are options to configure the appearance of your legend.
This can be accessed from the last option on the left-hand side on the screen for Legends and Flyouts.
There are a number of different options in this section to control the look and appearance of your legend.
By default this will be selected, this option will allow you to completely remove the legend from your visualization.
Next, you have the choice between two options: Overlay Legend and Inline Legend.
This will create a Legend button on the bottom left on the visualization that can be expanded on by clicking. You also have the option for the legend to be open by default for any user viewing the visualization.
You also have the (new) option to show the legend inline, so that is is part of your chart. You can choose it to show either on the left or the right of your visualization. The image below shows an example of the legend set inline.