Pour it into the pan or tray in which you will make the cake and spread well with a spoon.
By the way, the tray - I took a cake tray with removable walls (28cm) and I had problems with it - when baking the caramel and the juice leaked from it in the oven, so I had smoke and fun afterwards.
Be careful to take a tray or pan that will not leak when baking, or put the tray with removable walls in a flat oven tray - it will flow, but not in the oven, easier to wash the tray than the oven :)