Use a simple brief: what you are trying to do, the information the assistant should use, and the kind of result you want. You do not need special phrases or an elaborate role description to begin.
For example, explain that you are organizing a small community event, provide the activities and time available, and ask for a simple draft schedule using only those details. Review the result for missing transitions or unrealistic timing. A clear, ordinary request makes it easier to see whether the tool understood the job.