First, make sure that your sauce has been cooled to room temperature. If you want to use it as a layer on the cheesecake, not just a drizzle on a slice, it needs to be cooled. Next, bake your cheesecake, remove it from the oven and let it cool. Finally, while the cheesecake is still in the springform pan, fully cooled, top it with the sauce and refrigerate for 6-8 hours. You can add it later, before serving, but it won't get a chance to settle nicely on top of the cake. Another tip is if you plan on using it as a cheesecake topping, make sure to thicken it with the cornstarch slurry. Hence, the mixture will be thicker and look better on top of the cake.