How to manually write an element of group ring in GAP.

Question

Suppose, we consider

R:=GL(29); (Galois field of order $29$)

G:=SmallGroup(7,1); (cyclic group of order $7$)

H:=Group Ring(R, G); (this generates the group ring).

Suppose that GAP is unable to fetch the list of elements.

Then how can I do the following:

(i) check whether an element is in H or not and how to write that element.

(ii) how to select some element of H, let's say $n$th element.