How do I reserve the chapel on a Saturday for choir practice?

There are two options:

If you are a calendar editor, you can schedule it yourself. You could ask a calendar administrator (your ward clerk, for example), if that is an appropriate request.
You could ask any calendar editor or administrator to schedule the event for you (again, your ward clerk is a good place to start)

[Moderator Notes: I moved this thread from the Directory forum section to the Calendar section.]

Questions that can benefit the larger community should be asked in a public forum, not a private message.