For the Comparison field, select how you would like to compare the fields.
Type in $post$ in the Value field to pick up the post ID.
Click Update to save your Post Selection.
Note: adding more than one Rule will create a relation to control how field rules will be joined within the meta query with AND or OR.
Note: Do you want to customize a query (WP_Query) that is used to get posts for a Post Selection, but the option is missing in the UI? Continue reading about the Post Selection Filters.