How do I mark the subject and predicate

The subject (подлежащее) is the part of the sentence that performs the action or is described. It usually answers "who?" or "what?". The predicate (сказуемое) is the part of the sentence that describes the action or state of the subject. It usually answers "what is the subject doing?" or "what is the subject like?".

To mark the subject, you typically underline it once. To mark the predicate, you underline it twice.

Example:
Лучи (subject) освещают (predicate) его.
Туман (subject) синеет (predicate).