How to install what where?
The .txt file? Kinda varies from phone to phone, probably plug in your phone, navigate to the Notes folder and copy it in there if the device supports non – video / music / picture file copying. Other ways include connecting to a CIFS / NFS share if you have a NAS on the network, or even visiting the forum on your phone and downloading it directly.
How to “install” root on your phone? The difficulty and specific instructions vary wildly between devices, if you don’t have root access you’ll need to research that one yourself.