You can only find this free battlestar after unlocking the Showdown Loading Screen.
This is the Showdown Loading Screen for reference:
There is a battle taking place, but look at the graffiti in the background...
There is a red crab spray painted on the brick wall in the background. A battlestar is seen spraypainted above the crab.
See screenshots and maps below to help find the location of the secret battlestar.
- You can only locate the week 5 star after you have unlocked the Showdown Load Screen.