Implement a shared memory between nios2 and VHDL

Hi

I just got started with nios 2 and quartus about 2 months ago. I need help on how to share variables between nios two and the VHDL within quartus. For example, I got an array caller 'a[50]'. I want to be able to read that variable in the VHDL side. Can you explain to me step by step please. Also explain to me how would I wire it in qsys and call the function in vhdl? Would I need shared memory and how would I use it?

Thanks