Open Cookie Clicker
Press F12 or Ctrl+Shift+I to open Developer Tools
Go to the Console tab
Type `Game.cookies = Infinity`
Press Enter
Type `Game.cookiesPs = Infinity`
Press Enter
Type `Game.cookiesEarned = Infinity`
Press Enter
Type `Game.cookiesReset = Infinity`
Press Enter
Type `Game.HowMuchPrestige = function(){return Infinity}`
Press Enter
Type `Game.cookies = 999999999999999999999`
Press Enter