Root - Lenovo Sisley S90-a

Rooting is the process of allowing users of smartphones, tablets and other devices running the Android mobile operating system to attain privileged control (known as root access) over various Android subsystems. As Android uses the Linux kernel, rooting an Android device gives similar access to administrative (superuser) permissions as on Linux or any other Unix-like operating system such as FreeBSD or OS X.
Rooting is often performed with the goal of overcoming limitations that carriers and hardware manufacturers put on some devices. Thus, rooting gives the ability (or permission) to alter or replace system applications and settings, run specialized applications ("apps") that require administrator-level permissions, or perform other operations that are otherwise inaccessible to a normal Android user. On Android, rooting can also facilitate the complete removal and replacement of the device's operating system, usually with a more recent release of its current operating system.



Before anything else, check the current firmware on your device.
Go to Settings > About Phone > Device Information and see on the Android Version.

This tutorial is strictly for Kitkat Firmware (version 4.4.4) only:

Option1:

• Download the Kingroot.apk from here.
• Allow installation of applications from unknown resource.
•  Go to Settings > Security > "Check" unknown resource.
• Install the downloaded application.
• Open the app and Start/Root.
• Done.

The application itself will tell you when the rooting process is done. So be patient.
Note: There are cases that the unit will reboot so don't panic.


OPTION 2:

• This can only be accomplish after unlocking bootloader.
• Download the S90.bat file and extract it to your computer.
• Preferably on the root folder of Local C:
• Locate and run the S90.bat (and a command prompt will show)
• Wait for the process to be done. Your unit will reboot at when rooting is process is complete.
• Done.

Credits:
I don't own any copy of the process that are said above.  All of the tutorials on this blog are just from different developers worldwide. all credits are on the owner.