Open Messenger. Enter your phone number and Facebook password. Due to the old version, you may be prompted for a login code (2FA). Enter it, and you are live.
Using a 4-year-old APK on a 10-year-old operating system is risky. Before you proceed, understand these three dangers: facebook messenger for android 4.4 2 apk
The era of Android KitKat was glorious, but time moves on. This legacy APK is a stopgap, not a permanent solution. Enjoy your retro device while it lasts, but start planning your upgrade. Open Messenger
To summarize your action plan: