twrp 126.96.36.199 or later is recommend.
Goto CM 12.1 website and download the latest 5.1 Gapps here
Install: 1) If you are coming from any other firmware go to TWRP Recovery, on the menu Wipe and wipe: Cache, Dalwik Cache, Factory Reset (delete all your data and apps), System (remove the currently installed system). After that Reboot -> Go back to recovery Select Install and select the Rom file, Select Add More Zips, choose the 5.1 Gapps you downloaded, and flash the rom.
ScreenCast Does not work. The problem is in the HDCP