Theme Horse

Hi Martin,
Go to Appearance->Theme Options->Featured Posts/Pages slider->slider options
Set the number of sliders and other transition effects.
Then go to featured post/page slider options below slider options
Fill each input box with the Post/Page ID of the post/page which you want to use as slider.
You can view Post ID by clicking Posts/Pages->All posts/pages in your Dashboard. Hover the Edit link on individual Post/Page there you can see the digit value of the Post ID.
Remember that each post whose post/page id you are using for slider must have featured image minimum of size 978(width in px) and height (recommended 440px) according to your choice for slider image to show properly(Note: Better to use all images of same size.)
After filling all input box with Post/Page ID click save.

There is also other options to add slider and also you may use revolution slider which is also our demo site of ultimate pro.
If you like to remove the featured text then Go to Appearance -> Theme Options -> Design Options Tab -> Custom CSS paste the following CSS code and Click on save all changes button:

.featured-text {
display: none;
}

Please provide your site url too.

Thank you!