A single ASA 5515-X running ASA software 9.5(1) or later can run FirePOWER module with FirePOWER software 6.0 and be managed by ASDM.
The FirePOWER (sfr) module is supported as of ASA 9.2(2) but needed FireSIGHT Management Center (external VM or appliance and separately licensed) until ASA 9.5(1).
Check if you have the SSD:
show inventory
...and what software module (if any) is installed:
show module
If you don't have the SSD, then order it. If you have the SSD but not sfr module then install it (see Quick Start Guide). You also need Control (CTRL) license (no cost item). You will then need to decide on software IPS, URL Filtering, AMP or two or three of those and what license term you want (1, 3 and 5 years are the choices). Your partner or reseller can provide all of the part numbers and costs.
With everything in hand, follow the quick start guide.
http://www.cisco.com/c/en/us/td/docs/security/asa/quick_start/sfr/firepower-qsg.html
Once it is all setup, create and deploy policies. A couple of guides are in these locations:
Cisco Live presentation BRKSEC-2018 from San Jose 2015 at www.ciscolive365.com
Lab Minutes videos free here: http://labminutes.com/video/sec/ASA%20FirePower
