1.You should have Custom recovery installed on your device.
2. Make Backup of your current rom before flashing this Rom.
I AM NOT RESPONSIBLE FOR ANY DAMAGE CAUSED TO YOUR DEVICE. Do it on your own risk.Follow the instructions properly.
#How to install Cyanogenmod 13 Rom in Galaxy Express 2
1.Download official CM13 Rom and the appropriate Gapps 6.0 from below.
2.Now place the Cyanogenmod 13 rom and gapps 6.0 zip file in sd card .
3.Now reboot to TWRP Recovery mode
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!