The promotion was specific to the Epic Games Store only, not the Steam version which won’t be available until 2021 due to Epic exclusivity. Rob Bartholomew, Chief Product Officer, expressed his excitement in a press release earlier,
“We were optimistic but we couldn't have predicted this level of excitement. It's been incredible to work with Epic on giving this brand new release away for free. Now we get to welcome so many strategy players – new and old – to experience this incredible Saga. We're very happy."
If you missed out on the free period, you can buy the game on the Epic Games Store for $49.99. If you missed it, be sure to check out our review.