Right click on the taskbar ( blue colored bar) on top, uncheck "lock the taskbar". If there is a tick, click "Lock the Taskbar" to untick it.
If it's already unchecked (no tick mark in the box next to it) then just right click on the task bar and "drag and drop" to the bottom of your screen. That is, drag your mouse while keeping the fore-finger pressed on the left button.
That should do it