How do I change the aspect ratio of my recording in the Record Studio?

You can change the aspect ratio of your recording in the Record Studio by selecting the Ratio button in the inspector toolbar above the canvas.

The ratios you can select are:

Select the ratio that you would like to change your recording to - the changes will apply automatically.

You can further customize the layout of your recording based on the ratio selected. Read how at How do I customize the appearance of my recording in the Record Studio?