Workout Bench form?

I finally got a workout bench I've been working out/lifting for about 4 years and although I can do everything from the floor I felt like I was missing some range of motion, my aldis had one for sale and I grabbed it, my issue is when I lay flat to do a chest fly I can't get my feet flat on the floor and so I feel like my lower back is arched can I bring my feet up onto the bench? Does anyone have proper form suggestions for this?