This is one in an ongoing series of posts to help you hone your skills as a speaker either in an up-front setting or a small group.
I can't tell you how many times I have heard Louie Giglio's talk, How Great is Our God, the one with the planets and the cross-shaped molecule, and only once has a person actually given him credit. Besides the obvious moral problem, you are not Louie Giglio. You will almost never be as effective giving someone else’s talk as you will giving an original.
There’s nothing wrong with using source material and even those prefab talks you get in a lot of ministry products, but make them your own. Change the order, illustrations, and wording so that it makes sense to you. And please, please give Louie credit for his amazing work. If by some fluke, you are one of the few that have not heard this talk "borrowed" (without credit) you should check out Laminin... it is really interesting!