add items to Carousel on runtime

I have a picturebox1 and radtextbox1 radbutton1

I show pictures in picturebox1 from file

I need to click radbutton1 to add image from picturebox1 ,and text from radtextbox1 above it and resize image to 8.27 inches width , 11.69 height stretch

I could add the item but the big images appear so big 

I used this code in radbutton1 click event :

Image image = pictureBox1.Image;
            RadButtonElement item = new RadButtonElement();
            item.Image = image;
            item.Text = radtextbox1.Text;
            radCarousel1.Items.Add(item);