There is no procedure which automatically adds a paramater,
but it is easy to write one via
the ringlist command:
convert the ring into a list
list L=ringlist(r);
modilfy the first entry
and create a ring from the changed list:
def r_with_paramater=ring(L);
The help to ringlist gives examples:
http://www.singular.uni-kl.de/Manual/3-0-1/sing_274.htm