I have installed 3-F Gripper with UR10 mechanically and have also completed connections of Power and Communication Lines. Both Blue and Green LED are glowing continuously. Even using MODBUS, I am able to jog gripper. 
However, I am not able to figure out how to operate this gripper using UR10 Teach Pendant through a program. I have downloaded the files from UR Kit from your website and have installed it on UR. (While installation it shows 2-F Gripper being installed, I don't know why?)
While trying programs from the word document of same UR Kit. It shows errors like "function rq_close is double defined".
Could you please provide some guidance on how to solve this problem and any step by step guide on how to program it with UR.

No, there is no 2-F URCap installed and also it doesn't show under URCap screen tab.
I started programming using the guide that you provided in the link. But it showed errors like "function rq_close is double defined". I don't know how to overcome such errors.

Now, I could solve the problem to some extent. I would like to request you to make following changes for better convenience of other users-

1. While installation is in progress, screen message reads as 2 Finger gripper being installed. Whereas, actually 3 finger gripper is being installed. Therefore, I would request you to make a change in this to avoid confusion.

2. The file named "rq_3FG.installation" changes the safety settings of UR10 robot, which doesn't allow the robot to function. Therefore, We have to use default files.

3. Your document recommends using "rq_3FG_api.script" file as BeforeStart file and also calls subprograms using their script files. Which leads to the double definition of functions and results in error. Therefore, one should either call functions from "rq_3FG_api.script" or use subprograms not both. Please, update the document.

I hope this helps other users.

Thank you @Shivam_Dubey for this detailed update.