There are two ways to resize any element on your site:
Clicking and Dragging the element itself
You are able to click and drag from the corner or side of any element to resize it. You will see the element grow or shrink as you move your mouse.
Using the Design Panel
You are able to input specific pixel dimensions into the Design Panel next to the W and H options.
W stands for width, while H stands for height.
The Width and Height are automatically linked together, Unclick the link icon to individually change width and height of your element.