You should not overwrite the system vimrc for various reasons. One being that with a system upgrade it will be overwritten.
Instead you can create a new .vimrc file in your home directory. Open the terminal and enter:
vim ~/.vimrc
There you can enter your various configurations. When done, you need to save the file and restart vim.
To be sure which vimrc is being used, you can ask inside of vim by typing:
:echo $MYVIMRC