Go to cisco's download page, and select the latest ASDM image

Open ASDM, click on Tools (1), then File Management (2), 

Under File Transfer (1), select Between Local PC and Flash (2)

and transfer the ASDM x.x.x image (1) to the Disk0 (2) or the pertinent Disk, then transfer the file(3).

 
Save the configuration

From the Command Line interface of the ASA

shut down the current ASDM, go to the firewalls web page and download the new ASDM to run.

Also in the following link you can see the asdm compatibility information
http://www.cisco.com/c/en/us/td/docs/security/asa/compatibility/asamatrx.html