The goal of Politicle is to guess the mystery congressmember in as few guesses as possible.
To start, enter a congressmember in the search box and select your choice. Below the search box, you'll see the representative you guessed, along with a with a number representing the difference between the ideology of the mystery congressmember and the representative you guessed. These similarity scores are based on NOMINATE scores, which come from here. You can read the Wikipedia on this type of scoring here. A positive difference indicates that your guess was too liberal, while a negative difference indicates that your guess was too conservative.
You can also take advantage of some hints. Click the 'Want a hint?' button and find out the mystery congressmember's chamber, birth year, or the number of electoral votes their state has.
Keep guessing until you get closer to, and eventually find, the mystery congressmember. Good luck!