There are a few different methods to apply this tool.
You can create contemporaneous notes or memos to keep as references for yourself where you summarize the new encounter, mentioning who the person is, where you met, and what you discussed. These notes or memos can be kept stored in a file or sent in messages to yourself in a chat box.
You can also include the other person in your recap by sending friend requests on social media or, if you get their contact information, by following up with an email or text. The message should be short and to the point. Remind the person how you met, who you are, and what you spoke about. Tell them you were glad you met and that you look forward to connecting in the future.