Sorting an array of length $n$ in $O(m+n)$ time

Question

I need to find a method to sort an array in $O(m+n)$ time complexity. I understand it should be a variation on Radix sort, however I am not familiar with it or its implementation...

Input: an array $A$ of length $n$, containing values from $-m$ to $m$

Output: a sorted array $A$

Any suggestions will be appreciated, thanks!