When To Talk About Exclusivity?

I (26F) have been talking to a guy (26M) for over two months now. Things have been great for the most part, he's attentive, thoughtful, and I genuinely like him as a person. But I can't help but feel a little insecure about where I stand with him. How do I bring up the idea of exclusivity? Is this something that you do in person or over text?

I've never been in a relationship so I'm unsure of how this works 😅