Adapt program to suit Arduino UNO
You'll be wasting your time tring to convert the code on a procedure by procedure basis.  Arduino has different libraries, different clocks, different pins, etc.

I suggest you flowchart the code, and then work out which of the Arduino libraries (SPI, LCD, etc.) you can use to achieve the flow.  You'll be able to drop some of the initialisation code probably as Arduino is easier to run "out the box".

There's no quick-and-easy solution here - it's a re-write... as you'll find is often the case migrating code from one MCU to another.