I need to know if I'm on the right track...?

I need to loose 30-40 pounds by mid september....I'm starting with my elliptical [30 min a day], doing 15 push ups and sit ups. I'll gradually increase the numbers...but I have flabby and fat arms...apart from the push ups, what else can I do? Oh I do have dumbbells but I don't know what to do with them...oh and Butt exercises...any suggestions???