If your content is relatively simple – text, images, links etc. – you can easily create an article and restrict it to one or more memberships. Then, this article will just appear under the regular ARTICLES menu option.
To create a simple article like this, you need to do it under the POSTS menu option. A POST is just an article. End users think in terms of “articles” and admins tend to think of terms of “posts”, hence the slight discrepancy in the terminology.
To create a simple article and restrict it to one or more memberships:
For most use cases, this is all that’s needed.