The slideshow should come from the most recent post you have. On the right hand side of the post editor there are some boxes for Featured Image options. One of them is labeled Featured Images, you'll need to hit Insert Image and add your photo that way. Then save and view the home page again.
Make sure that in your Habitat Option>Slideshow Options the first dropdown is set to "First Entry with Fullwidth picture".
As for the titles, you'll need to use the html character codes for the letters you'd like to have with accents. Just be aware that not all the fonts available under the main options> Heading Font support these characters so they may show up blank unless you choose a different font. In my quick test, not selecting anything and leaving the dropdown as "Select..." with the post title "Café au Lait" produced the proper "Café au Lait" on the front end.