By default, the posts and content you create are added to your 'follow' list.
You can add more posts or categories by selecting 'follow post' or 'follow category' from the menu on each post or category (it's the little three dots on the top right-hand side).
If you're no longer interested in receiving notifications when activity or updates have occurred in those posts or categories, the reverse applies. Use the same steps and choose 'unfollow'.