Hi Laura,
Assuming that you are referring to a scenario where your client is trying to enter inventory or non-inventory items, this is possible in the "home" screen under the items tab link. To add an inventory item, below the existing items grid screen hit the new... button. This, of course, means your client does not require access to the QB databse, as they can do this directly through method. If you are referring to something different, kindly provide further details on what your client is trying to accomplish, but I hope this addresses your question.
Regards,
Denis