If your activities are attached to a program (you can see the badge when previewing a program) then they will not be able to be completed until the first day of the program by a reader. Staff will still be able to complete activities on a reader's behalf, before or after program/challenge dates.
If you have repeatable activities or activities not attached at the program level, then you can do one of two things. You do not have to do both!
1. Go to Content > Learning Tracks (aka Activities, Activity Tracks, Activity Badges), then edit the track so that it is available to "Staff Only." You can do this by selecting the pencil icon next to the badge, and then selecting "staff only."
2. Go to Content > Learning Tracks (aka Activities, Activity Tracks), and ensure that the track is not showing (un-check the box pictured below).