We have 2 options.

1- Make any category to Featured:  All ads from that category will be shown in premium ads.

For this option, visit this link.

https://joinwebs.ticksy.com/article/6306/

2- Single Post show at Premium Slider: If you want to show a single post on Premium Slider, Then please go to

WordPress Dashboard --> All Posts --> From here first find that post which you want to show at Premium Slider, Then edit that post.

And you will see Option to Make it featured in Sidebar.

Just check that options so it will be shown at premium Place.

3- Make Featured with Plans: If you have post a regular ad, And now you have purchased Ads Plan and you want to make that regular ads to Paid ads. 

Then from front-end Just Visit your Profile (User Dashboard) Page, Here you will see your all ads, Just click on Edit Post, Then come to very bottom, You will see Regular ads is checked, And there will be one another option for Premium Ads.

Just check that option and update Ads.

Thanks