Change the size of an object by selecting the object in your Work Area then clicking and dragging one of the black square handles to reduce or enlarge it as desired.
Learn about resizing by defining precise dimensions: https://smartdraw.zendesk.com/hc/en-us/articles/360042886271-Sizing-with-Dimensions
Make all shapes the same size: https://smartdraw.zendesk.com/hc/en-us/articles/360042761391-Make-Same