Its best to start with taking it in the morning. Start off with a couple of drops under your tongue and swallow. Some believe that the sensors under the tongue read it and there have been studies that say it is somewhere in the back of the throat that does. Best to do both just in case. Once you get used to the taste start taking more and more of the morning urine, and if you'd like better/faster results the clearer urine throughout the day.
A couple of tips. If every time you pass urine you put a couple drops under the tongue it will become clearer and clearer. If you eat salt it will be salty if not it wont. Meat it will be bitter, fruit it will be sweet. Practicing looping (taking a little or all that you pass through the day) you'll notice it becomes so clear and easy to take. Some people say while practicing UT if they take it after 8pm or so it keeps them up at night. You will notice it will lift your mood quite a bit. It's not good to practice ut while on medications though, because some of these things can be recycled and with some things this is not good. If you're on any kind of medications consider some herbal alternatives, but get off any medications before taking those! Be well