Erlang array vs list

I'm new to Erlang so I am working on an example program and struggling to decide whether I should use an array or a list. Both are easy to create and handle but I didn't get: How you append an item to an array without knowing an index of where it should be appended. Is array:set(array:size(A),"a",A) the way to go? How to find out if a certain element is a member of the array, just as the lists:mem

[Jxck]

lists と array の違い なるほど “Lists are a data type that is native to the Erlang VM. Arrays are implemented as a structure of nested tuples. ”