You can send a PM by clicking on the user's forum name on the right of your screen, and navigating the page to where it says PM: Send private message. From there, you can type out what you want and I believe as long as you want the message to be. I'm not sure if there's a restriction on posts in order to send the PM like most forums have, so you'll have to just try it out and see what it says. If that's the case, then I'm sorry.
If you need anything else pal, feel free to get in contact with me IG with the name Robert OBrian,
or get ahold of me on the teamspeak (ts.redcountyrp.com) with the name TempestFox.
Or just simply reply back here and we'll sort you out