SIgn BOL is available only after you completed the inspection! It's required to take at least 1 picture of the vehicle or mark damages on the diagram.
When Car Inspection is finished, you will see a popup offering you to Complete eBOL, select it. 
A person's name is required. Hand your device to the customer to sign it.
The eBOL can be signed and sent to a shipper or receiver by Email or FAX. For that type the email address or fax under the name.
Select Sign to generate eBOL and send it.
Use "Not Available" or "Refused" in case Shipper or Receiver is not at the pickup or delivery point or they refused to sign. You will generate a good-looking BOL with a time stamp and protect yourself with Inspection pictures with time and location stamps.