How to allow dublicate Category Posts

I have the below problem:
– I have 2 categories:
1. News
2. Featured News
– In my main page i dipict 10 of the posts from “News” Category.
– Some of these posts are also asigned in “Featured News” Category.
– I use “WP Content Slide” which gets the category’s “Featured News” posts.
– The problem is that if a post is assigned in “Featured News” and in “News” categories, it cannot be displayed in main page posts but only “WP Content Slide”.

How can i fix it and these posts (assigned in both categories) can be displayed in Main page and in “WP Content Slide”?

Thanks in advance