"Am with it" can be synonymous with "I understand", "I get it", "I'm on board", "I agree", "I'm in sync", and "I'm on the same page". All of these expressions suggest a level of comprehension and agreement with a certain idea or situation. They convey a sense of being present and engaged in the discussion or activity at hand. Using these synonyms can help establish clear communication and ensure that everyone is on the same wavelength. Whether in personal or professional settings, it's important to convey that you are fully present and engaged in the conversation or task at hand.