script for controlling player

Hello

I am trying to develop a demo for displaying CBCT segmentation data. I precise that I am not a IT guy and quite fare from being proficient with a computer. I am learning Csharp and unity side by side on my free time, but as expected I encounter a lot of problem along the way

This my progress so fare

I use existing software for realizing a segmentation ( creating a 3D object ) from a CBCT, so fare I had to try several until I found one with good functionality. Had to spend some time learning how to use it also (still learning)
I then use 3Dmesh to convert my 3D file into a format that I can import in unity.

I was able to create a small demo to see 3D object but I have some trouble with the control.

- my character can only walk and I would need to have him fly (in fact just go up and down would be perfect) and stay in midair when no control are activated.
How can I modify the script to do this ? I try to modify the input in unity to make two key active along the Y axis but nothing happen, which is normal as I did not edited the script of the player yet.
I understood that I have to change the part on vector3 ( the value on the middle being set to zero currently) and probably set the gravity to zero.

Any suggestion ?