If you already have the Settings screen displayed, click on the Taskbar item on the left:
If you can't see a settings screen, you can bring it up by clicking on the Settings item on the Start menu (bottom left of your desktop screen):
When you click on Settings, the screen may look like this at first:
Click on the Personalisation item to go to the settings screen. Then click the Taskbar item on the left:
Most of the items on the Taskbar list are toggle switches. So, for example, if you want to automatically hide the taskbar at the bottom of the screen, click the toggle to turn this item on:
If you look at the bottom item in the image above, you'll see an option to "Use Peek to preview the desktop … ". This is what we turned on to get a preview of running apps. Click on the toggle switch to turn this item on, and it will turn blue.
If you want to squeeze more items onto your taskbar, toggle the Use small taskbar buttons item. The effect is this:
Notice that the Cortana search box has now turned into a white circle.
Although the taskbar is at the bottom by default, you can change this. You can have your taskbar at the top of your screen, or on the sides. To do this, scroll down until you come to the section called Taskbar location on screen. Click the dropdown list to see the following options:
So you can select Bottom, Left, Right and Top. Try it out to see what it looks like.