bit of a long convoluted way to get this, not like all the other free stuff on epic, bit more work involved, total war access account, linking, email to click and so on.

https://www.totalwar.com/blog/a-tota...y-amazons-faq/

WHERE DO I SIGN UP FOR TOTAL WAR ACCESS?
From the 24th of September 2020, go to https://www.totalwar.com/access-amazons/.

Fill in the form to create your free account and follow the instructions that will be emailed to you in order to complete registration.

Be sure to tick both boxes in the registration form to hear about the latest news and exclusive offers for all Total War games!

WHAT DO I DO ONCE I HAVE A TOTAL WAR ACCESS ACCOUNT?
Once you’re logged in to Total War Access, head over to https://dashboard.totalwar.com/home/troy-amazons and click Claim Code. Your product code should appear below the banner for Amazons. Copy the code and click Redeem here: Epic Games.
HOW LONG WILL AMAZONS BE FREE?
Amazons will be free to claim from the 24th of September to the 8th of October 2020. If you claim the DLC during this time, it is free to keep. You’ll have until the 5th of November to apply your product code to your account.

then when you look at your EPIC library, the total war troy should have '1 Addon' icon on top of it and ion the store page 'owned'. £7.99 otherwise.

unsure whether you can add DLCs to epic account if you don't own the base game, like on steam, but i'm assuming everyone owns this game already, seen as it was free on launch day