How to get retinues?

[Ambigore]

I got the LoR add-on and have noticed that a few of my vassals have 500-man retinues. I'm playing as the King of Cumania with the CK2+ mod. It's about 30 years since the start of the game but I don't seem to have an option of creating retinues? Can anyone explain to me how to get them, or what requirements would I need to meet? My Military Organisation tech is at 0, but I noticed that my vassals who have retinues also have 0 tech as well.

 

[unmerged(600321)]

Retinues are available at the start of the game. No tech is needed. They are just in a new tab on your military screen (where the levies are). If you are small though, you won't be able to get any retinues, since even the smaller retinues take "600" retinue supply. You won't start off with 600 if you make a count for instance. But as you grow, you will have the room to create retinues.