The verb is underlined; it's an imperative verb, a command, so the subject is implied (you):
1. To request that email notification begin, click "Request Change of Address" above.
Note, the verb request takes a subjunctive verb (i.e., begin, not begins)
2a. What are these two things: (1) the subject and (2) the verb?
2b. What is the subject and (what is) the verb?
Note, for sentence 1., I'd use, "What's the subject, and what's the verb?