Using commercials fonts?

Hi,
I have probably a very stupid question regarding the usage of commercial fonts in logos. But I would really be glad for any reply.

How do I use a commercial font? :huh:
Details: I’d like to use “trajan pro” in a logotype. But I’ve never done this before, so I don’t know how it works. Is it sufficient when I buy the font, or does the company have to buy the font, or has noone to buy the font :slight_smile:

Thanks,
Michael