iOS 8 doesn't come with Myanmar Font. So, if you want to read Myanmar text in native app such as Facebook app, email and note etc.. you need to install ZawGyi font.
To install ZawGyi Font for iOS 8, visit the following link using safari browser. http://shwe.co/zawgyi
Figure (1) - Visit http://shwe.co/zawgyi using safari browser
Figure (2) - Click Install
Figure (3) - Click Install to install the font
Figure (1) Figure (2) Figure (3)
That's all you need to do and ZawGyi font can be used by App.
Notification Message, iOS Mail App, Facebook App, Notes etc can show the text in Myanmar Language.
If you want to type in Myanmar language, you may install ttkeyboard from app store.
It is just a keyboard and without ZawGyi font installed, you can't see what you type in Myanmar Language.