For the bottom, you will "squash" your shape down
Again, you need to fill it with a texture. The same way as you did with the umbrella.
You need 2 of these. You can choose EDIT/DUPLICATE OBJECT.
When you do this, it will lay a copy on top of your object (this is very handy!). Now you will make sure your first one is chosen to work on, if you have your side stack on, it will be the 2nd picture you see. You will need to trim this one in to an oval. Go to CUTOUTS & PICTURES/TRIM CUTOUT/CIRCLE. You can pull your rectangle up so you can see it all, choose the circle and make it an oval shape, then trim your shape. Now you need to make the other shape dark. Choose the 2nd shape and go to TOUCHUP/BRIGHTNESS & DONTRAST. Choose the BRIGHTNESS bar and take it to the far left. Don't make it black, but a darker color of the first color. You can see the color change as you move the bar back and forth. When you are done, you will place the light colored top onto the bottom
You can bevel them to make them look fancy.(see my tut on beveling!).