how do I use indices on mathcad prime?

For example:

i:=1..5

Xi:=whatever, whatever, whatever

Yi:=whatever, whatever, whatever

It seems that this is a breeze on Mathcad 15, why can't I figure out how to do this on prime? Can it be done on Prime? I am taking a course in physical chemistry and don't know what to do about this. Should I download mathcad 15?

Thanks,

ABH