how do I import an excel spreadsheet to perform a compare?
In Toad/Oracle, the Import Wizard will allow you to import the Excel content to an Oracle table that you have built to receive that data. Then you can use the Data Compare facility to compare source and target. Note that this sequence of steps can be automated within Toad.
Alternatively, you could use Toad DataPoint to compare the Excel and Oracle table directly, and possibly eliminate the import step altogether. This work flow can also be automated.