Guided imagery is one of my favourite things. It's a bit like being told a story when you were a child. Although there isn't a story with a plot there is a thread of ideas and images for your mind to follow.
This thread will hopefully lead you away from the present and into a relaxed and open minded state. With a bit of luck you might even move from Beta wave to Alpha wave brain activity, maybe even more.
You don't have to "do" anything, just get comfortable and listen. If you can lie on a bed or sit in a comfortable chair so much the better. Just close your eyes and go with the flow.
Here's a completely free, no obligation example.
Don't listen to it if you are driving or doing anything else during which to fall asleep would be dangerous.