In alpha you got it from winning fights in the arena but not anymore? where can i get plate armour now?
You can get maille from Cumans and other Bandits. They also have Brigandine and Lamellar cuirass.
Apart from looting from the final battle there are no legitimate areas you can obtain plate, but you can kill and loot either a wandering soldier from the camp, or move outside the fence and snaffle some from the ‘river bank’ to the west of Samopesh.
Cuirass and Chausse are relatively hard to come by, but couters and vambraces are more common, and helmets are near universal. I actually find that I cannot equip a full set of armour (weight considerations, except when using squire), but have to pick a choose a bit.
thanks. ill have to do the battle then. wont i get attacked for looting?
I don’t know. Maybe. Fun isn’t it 
Incidentally plate isn’t always superior in protection or weight to brigandine as currently listed.
Easiest way to get armor.
Those are the ones to the West of the Samopesh fence that I mention above.
how would full plate be inferior to a brigandine?
The ‘blunt impact’ values as listed are slightly weaker in direct comparison of some cuirass and other items (though there are also several qualities of some armour types, so this may not be directly like for like (i.e. good brigandine vs weak harness). These are only placeholder in-game stats, so may change over time, but I was only pointing out the need to watch the three armour values when electing to use any armour type over another - maybe along with coverage on the 3d model ?)
The same way that a mail coif weighs 16kg, or what ever that weight number is supposed to be. Game logic. In the case of the brigandine legs, their stats are identical to plate, with the exception of one stat, where they offer one point more of protection.
Of course they are also ugly and don’t match the rest of my outfit in the cutscenes, and you never seem to get hit in the legs anyway, so I went with full plate.