Your sheet will automatically be set to the “Free Size”, which means that your sheet will expand to the size of whatever you create. If you have a set size in mind, change your sheet size from free to the option that best suits your needs.

 

If you select “Custom”, you can set the width and height options yourself in the fields next to this setting.

 

 

Information on setting the diagram size on Editor versions before 6/27/18: https://support.cacoo.com/hc/en-us/articles/207910297-Setting-the-size-of-a-diagram