Try it as is first. It may already have a vld stem in it. If not, HORNADY sells stems for the eld bullets. They're about $12 or so. I just got one from Midway. If the seater in the die doesn't mark your bullets, don't worry about it.
That die set comes with 2 seating stems. One works ok for the ELD-X, but leaves a tiny mark (ring). In a bind, it will be fine for a non-compressed load.
As mentioned, Hornady does make one you can buy for the ELD-X /147 ELD-M. It works perfect.