New castles

How do you I take a free castle, any help would be appreciated.

Normal players can conquer them- attack the castle with silver to conquer it.
(Silver cost =1000*( your number of castles + your fortresses*5+ your cities*25))

If you only have one castle then it should cost 1000 silver to conquer the other castle. (the amount needed should also be displayed when you are selecting troops and resources to send for your attack).

Later if you get a ruby then you can conquer castle using 1 ruby instead of the silver cost.

If you have money then you can buy one for 3000 gold (constant price except during some sales).

https://xyrality.helpshift.com/a/lords-knights/?p=web&s=resources-gold-payments&f=what-is-silver-and-where-do-i-get-it

^ forum about silver.

Also if your conquest fails (e.g. against another player) then you lose your silver.