Hello,
If you already have an ASA running with CX module, please refer the following link and uninstall the existing CX module.If your ASA version is not compatible with the Firepower integration you can upgrade the ASA version . All the OS images will be available in the Cisco website software downloads sections.
http://www.cisco.com/c/en/us/support/docs/security/asa-firepower-services/118644-configure-firepower-00.html
Once its uninstalled integarte the Firepower module using the .pkg and .img files for installation.
You can access all the image files from the Cisco Software downloads section.
https://software.cisco.com/portal/pub/download/portal/select.html?&mdfid=286259687&softwareid=286271056
Rate and mark correct if the post helps you
Regards
Jetsy