Here is where you add what you found on ARC this week.
Keep in mind that learning this is an exercise that will serve you well when searching on OPA or the search engines of other archival facilities. This is particularly true when you are deciding what search terms to use.
You do not need to master ARC, because some day (sooner or later) it will be gone.
Using ARC while it is still available is a great way to experience the thinking behind archival description and some practice time spent here should help you understand ways in which records might be found in other archival search engines.