Hostile Takeover is the 6th Chapter/6th main story mission in Borderlands 3. It is unlocked when you complete the mission
Sanctuary. The recommended level should be around 12, and after this mission you unlock the ability to equip class mods.
For a readable version of the walkthrough: IGN's Wiki guide is the place to be.
https://www.ign.com/wikis/borderlands-3/Hostile_TakeoverFor those that need a more
visual
guide, check out this one by YouTuber "ZaFrostPet."