«Впервые» is an adverb you use to tell that something happens "for the first time" (that is the very firts time such thing happening). «Первые» is just neuter singular nominative of "первый" (the first). «здесь»(тут) is used to say where something/someone IS. Or where some action takes place. «сюда» is used to describe the DIRECTION of an action. It may be an outright verb of motion ("иди сюда!"=come here!) or some action that can have direction, like falling or pressing a button ("нажми сюда"=press here, "нажми на кнопку"=press a button). I don't know what you've learnt so far, but Russian in general distinguishes between the action happening somewhere and being directed somewhere. For example, with В/НА you use Prepositional (aka Locative) for location and Accusative for direction.

Тест :- Эти выходные - длинные. 26 января - День Австралии. 26th of January is Australia Day. Это день когда европейцы впервые приплыли сюда. It is when Europeans first arrived here.