How should you file electronically and specify more than one inventor?

If you have more than one inventor, then you will need to submit a Declaration form that allows for multiple inventor entries using the USPTO fillable form (SB02) or your own. In addition, you can submit the ADS (Application Data Sheet) PDF Fillable Form that will allow you to list multiple inventors, but the Declaration / Oath is the official record.

USPTO FAQ - Questions and Answers (31AUG2006)