Hello,
1. You can change images in slider settings. The dimensions of our demo images are 940px × 400px.
2. Those banners are added on your Home page with the code
<div class="banner one-half"><img src="[etheme_template_url]/images/assets/b1.jpg" alt="" />
[etheme_btn title="Shop Now" url="test_url" class="active"]</div>
<div class="banner one-half last"><img src="[etheme_template_url]/images/assets/b2.jpg" alt="" />
[etheme_btn title="Shop Now" url="test_url" class="active"]</div>
Go to Pages > Home and edit img src links to your images links.
3. You can create categories in Products > Categories and mark each product for the category.
Then you need add product categories to your menu in Appearance > Menus
https://www.8theme.com/blog/how-to-include-product-category-into-menu/
Thank you.
Regards,
Eva Kemp.