Ho can I get these images to appear in random spots on the page?

I am creating a collage app that has an dogAPI. When the breed is selected a dog image will appear. I want the image to appear in a random spot on the page but ideally not over the text and dropdown menu. This is what I have tried and here is my codepen. This is an app so it needs to also be responsive.

    //Get a random number
let getRandomNum = (num) => {
    return Math.floor(Math.random() * Math.floor(num));
}

//show image in a random location
let moveImg = () => {
    let dogImgs = document.querySelector('.dogPic')
    let w = window.innerWidth;
    let h = window.innerHeight;
    dogImgs.style.top = getRandomNum(w) + "px";
    dogImgs.style.left = getRandomNum(h) + "px";
};

https://codepen.io/drxl/pen/VwbQZyK