This sentence is in the present perfect tense. 'Have' is not a verb but an auxiliary verb.
Literal
This sentence [topic-は] present-perfect [copula-です]. 'have' [topic-は] verb [copula-ではなく], auxiliary-verb.
現在完了形 'present perfect tense.' The ~ではなく 'is not X but rather' construction clarifies a common student misconception. More English grammar metalanguage in Japanese — the kind of explanation found in a study guide.