1) Go to Slider Entries > Add New and type in the slide name, title, etc. Then add a featured image to each Slider Entry (will be used as slide/image). Click on “Set featured image” => “Upload” => Pick image => Use as featured image” on the slider entry editor page.
Then publish your slider entries.
2) Make sure that you use the default frontpage template – go to Settings > Reading and deselect any static frontpage.