Here's another suggestion:
If you are not currently utilizing the SOH "Flight Center" (see the drop down at the top of the page), then you need to, lol. All MP flights originate from the Flight Center. You need the latest Teamspeak Ver3 and FSHost Client Ver 1.1. Obviously, that also means that to use TeamSpeak you have to have a mic of some sort. . .either a headset/mic combo or a standalone desk mic and speakers. Flying in MP and trying to use the chatbox is something I don't do, it's not impossible, but that's the reason god invented Teamspeak, ok? lol.
You also need to take a look at the information in the Flight Center forums concerning the servers used for MP flights and for TS. I believe there is also a tutorial of sorts in there somewhere that explains the how's and why's of setting everything up. If you don't understand, post a question in the Flight Center forums so those folks can get you set up. The best scenario is to get online in TS, at that point you actually speak to a human being who can help you with anything else you need to know.
Finally, and most importantly, "port forwarding". For those who use a router, there are ports that must be forwarded in order to have them open while in MP. This can be tricky based on your individual setups, but be aware that if you don't bother, you'll probably get kicked off. Also, not forwarding the correct ports can cause other pilots to be unable to connect to the server, disrupting an otherwise good session. All that info is also found in the Flight Center forums.
Now is a good time to get the ball rolling if you don't presently fly MP.
Get FSHost Client here:
http://www.chocolatesoftware.com/fshost/
Get Team Speak V3 here:
http://www.teamspeak.com/
The basic setups are pretty straight forward. . .after that get the fine tuning done in the Flight Center. . .then get your ports forwarded (if necessary) and then try logging into FSHost Client and get flying.