Yes, you can. To obtain a key file use the same serial number that you've entered to receive a key file for your desktop anti-virus.
It is also possible to use an existing key file. To install the key, copy the drweb32.key file from your desktop computer into the Dr.Web installation folder on your mobile device (default location is C:\Data\DrWeb). This can be done via a direct connection to the PC or with a memory card.