Hello,
you'll find this easier to do with a sequence. Suppose your sequence is held in variable q, then you can write an action like
/\ q # << >>
/\ q' = Append(Tail(q), Head(q))
Moreover, an array (i.e., a function) with domain 1 .. N for some N \in Nat is just a sequence, so the same will work. If your array has a different domain, you'll have to write an explicit function definition, for which you may take inspiration from the definitions of Append, Tail, and Head in the standard Sequences module.
Stephan