A Property is one brand or client. Its ad accounts, targets and results live together in one place. If you run ads for one business, you need one Property. An agency usually makes one Property per client.
An ad account can belong to more than one Property, for example when one account runs ads for two brands. Link it from each Property's picker; the data is read once.
Everyone on your team sees every Property in your organization.
Archiving hides a Property and stops new insights for it. Nothing is deleted. Ad accounts that belong to no other active Property are disconnected, with their history kept. You can restore an archived Property from the dashboard and connect its accounts again.
Email bishop@battlebridge.com with the step you are on and the exact words of any error (a screenshot is perfect). A person reads it.