Once pressed, you should see a small tab open above showing you a list of units similar to the normal unit tab find the regiment of renown you want on this tab, and click it to acquire them.
However, with some regiments, you will need to progress to a certain point in the vortex campaign to unlock them other than that, in mortal empires, all you need to do is rank your lord to the required level. At this point, you can then recruit the newly unlocked regiment of renown by pressing the button to do so next to recruit units. To get regiments of renown in Warhammer Total War 2, you must first level your lord to a particular character rank at every rank all the way to rank 30, one regiment will unlock for you.
Regiments of Renown are unique units in Warhammer Total War 2, with both unique lore backgrounds and abilities, but how does one exactly acquire these famed regiments? How to recruit Regiments of Renown in Warhammer Total War 2
