First of all, create a rule to select the type of posts to be promoted. Select "type" for variable and set the operator to "eq" (equal) and then choose the post type you want to promote (you can choose between link,status, photo, etc.).
Now, let's create a new block of conditions by clicking on "add new block".
Change the relationship between the conditions in this block from "all" to "any". Doing so, any of the condition that we are going to specify will trigger the boost post action.
Add the conditions that identify the editorial line that you want to promote. For example, use the "message" variable with the "contains" operator and create a condition for each keyword or hashtag that you'll use for posts belonging to the same content area of your communication.
Now you can move forward by clicking "continue".