In polite English conversation, you can say, "Excuse me, could you please tell me where the restroom is?" or simply, "Excuse me, I need to use the restroom." This way, you are being courteous and respectful while conveying your need to go to the toilet. In English-speaking countries, people commonly use the term "restroom" or "bathroom" to refer to the place where they can use the toilet. Remember that using polite language is always appreciated in social interactions.