Decide how you will get in.

You find Sierra's house and catch a glimpse of the big titted nubian goddess walking past her window, so you know that she is home right now.

You feel feel your cock straining at your pants, but you're not quite there yet. You still need to get inside (the house first, and then Sierra).

You stand out by the street for a few minutes and then notice the storm clouds gathering above you. You'd better make your move soon.