Some responses, particularly requesting your submission code, are in the form of direct messages. To recieve direct messages from a Twitter user, you must follow that user. If you're not getting responses, make sure you're following the bot.
There's a tiny bit of flexibility for most commands. This is to make them easier to remember. Verbs like send are usually interchangable with tell and give. Also, words like me and my are usually optional.
send me my submission code- sends randomly-generated submission code, must be following the bot to get this message!submit {challenge name} {answer}- accepts submission, confirms if answer is correct if challenge is oversend me {challenge name} info- sends you the start and end dates for a challengecheck {challenge name}- tells you your previously submitted answer, and if it's correct- a few more ;), check the source