Clicking an Object on IPAD when within a Certain Distance

Hi,

I am working on a project for my university and need a little help with coding the interactivity of my APP for the IPAD. Right now I am working on making a GUI pop up when certain objects are clicked. I have figured out how to code the part that actually makes the GUI appear on the screen when clicked. I have the code working on the computer, web-based platform, however, when it goes onto the IPAD, which is my end goal, it will not let me click on the objects. Also, as of right now, I can click on any object from all the way across the room in the program.

I would greatly appreciate any help with these two problems:

1. A script for clicking objects on the IPAD touch screen that works using Unity functions

2. And a script that won't let the object be clicked until the character comes within a certain range.

Thank You ahead of time for any help you can give.