@Oliver4, do you mean you want to review a guest? Your dashboard will show who you need to review in the Pending section.
Do you mean you want to request that they review you? If a guest has left and it is within 14 days, go to your Inbox, where you will find a button under their message thread saying "Ask *** to write a review". I never use that, myself, as Airbnb asks them to do that, and I think me asking, too, will just be annoying. (If someone knows something new about that, as in this will now be the only request they get, maybe they will chime in here.)
Do you mean you want to find reviews you have written? Under the Host dropdown at the top of your screen, go to Reviews. There you can choose either Reviews About You or Reviews by You.
Hope this helps.