What to say when you want to introduce someone in Greek?
Well, here are the three basic ways!
Να σου συστήσω/ να σου γνωρίσω = let me introduce you to + name & article in accusative

Να σου συστήσω / γνωρίσω (τον φίλο μου) ΤΟΝ Κώστα – (τη φίλη μου) ΤΗΝ Ελένη. (In capital letters the article in accusative)

Από εδώ = in this context would be translated into = here is + the name in nominative

Από εδώ (ο φίλος μου) Ο ΚώσταΣ / (η φίλη μου) Η Ελένη (in capital letters the article in nominative and the ending of the masculine name)

Last but not least, the most simple way to introduce someone and the most informal is to just say the name of the person with the article in nominative or even without (depending on how friendly is the comunicative situation).

Ο Κώστας – Η Ελένη