Please go to appearance > widgets > portfolio featured area > drag and drop the main slider widget and save it.
You need to use portfolio featured area instead of page featured area because the portfolio page is your homepage.
I just deleted your homepage. I set up the portfolio page as a home page. On the right hand side of the page, there is a page featured area. I chose the portfolio featured area and saved it.
Hopefully, it will work for you.
Sorry the say but I am still having some trouble with the slider on my homepage on http://www.misvids.nl. When I don’t use any info on the slider the size is perfect. But when I start to add a text line and a link the slider is automatically changing in height. Something that isn’t happening on my other website: http://www.studiomima.nl
Do you know what’s causing this? I would like to have it fixed like the studiomime website.
I am almost finished, I really love the theme and I think after this I won’t bother you anymore ;-)