The shahada is the testimony 'La ilaha illa Allah, Muhammadun rasul Allah' — there is no god worthy of worship except Allah, and Muhammad is the Messenger of Allah. It affirms both the oneness of Allah and the prophethood of Muhammad ﷺ, and sincerely believing and declaring it is the entry into Islam.
References
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Informational, not a personal fatwa. Consult a qualified scholar for rulings on your situation.