When viewing a Customer's Account screen, the Orders section lists each Item in every Order. Clicking the Edit Icon returns the Edit Item screen. There is a variety of useful information, some of which can be modified by Administrators.
Locate the Account by logging into the Admin, clicking the Accounts tab, and searching for the Account in question (such as via the Account Holder's name or the Order Number), and clicking the Search Result.
You will see the Account. Click on the Order in question, and the then click the Edit Icon on the Order Item.

The Modal has detailed information about the Product, the Order, the Participant (if applicable), and the Product Participant Form (if applicable).

If Bibbing is setup for Race Events, a Bib number can be assigned to a Participant via the Edit Item screen, Input the Wave Code that the Participant will be in, then click the Add Icon.
The Participant will be assigned the next Bib in that Wave. Please Note: If you are holding a Race Event, and would like to use our Bibbling System, please give us a call and we would be happy to help you get setup.
If a Product Participant Form is assigned to Item that you are Editing, then you can modify that Form via the Edit Item screen. Make changes to the Answer fields, and then click the Save Changes button.
There is a Notes Icon at the top of the modal. The count of existing notes appears as a badge on the icon.
Click it to view, edit, or add notes. You can also delete them.

If you are holding an Racing Event, and if you have Bibbing enabled, then you can access the Edit Item screen directly from Race Advanced Search. Select your search variables, click Search Accounts, and then click the Edit Icon on the search result that you are interested in. 
As an added convenience, in addition to a "Save Changes" button, there is also a "Save Changes and Open Next" button. This button is useful when needing to modify a batch of Participants, such as to give them a Bib.