Stores don't have Wizards Accounts or DCI numbers; individuals do.
Each individual tournament organizer within your store (including store owners and managers) should have their own Wizards Account and password. This is what they will use to log into Wizards Event Reporter (WER).
Do not share your password with anyone. If your store has more than one T.O. (i.e. more than one person using WER), do not check WER's "Remember Me" box.
If you'd like to add more organizers to your store, you can do so by having them fill out the form on the My Store page.