The rom is quite stable as all the major functions are working.the only bugs are (NFC, continuous vibration (to stop press and hold power button), FM Radio, offline charging, and some others).Check XDA thread for latest download link and updated bug list.
1.Your device model must be Galaxy Ace 3 LTE GT-S7275 R/B/T.
2.Your device must have TWRP recovery installed to flash Cm13 rom in it.
3.Always make Backup of your data and current rom.
#How to Install CM 13 rom in Galaxy ACE 3 LTE
3.Now reboot to Recovery mode and flash Android marshmallow rom in your device.
4.Then flash CM13 android marshmallow rom and gapps from recovery in it.
5.Now Clear cache and Clear Data.
6.Reboot your device.Done! you just flash cyanogenmod 13 rom in your Samsung Galaxy Ace 3 LTE .Enjoy Android Marshmallow 6.0.