In The Sims Medieval, you need resources in order to build the buildings in the game. You normally get them by doing quests, but you can enter a cheat to set however many resources you want.
Hit Ctrl+Shift+C to bring up the cheat console at the top of the screen. Type in setkp followed by a number, then press enter to set your resources to that number. For example, if you type setkp 100 and press enter, you’ll now have 100 resources to build with.