Pmang is what is known as a games portal. There are several of these in Korea. They basically work as an aggregate site for some parent company to distribute and advertise the various games they have commissioned either in-house or through outside developers. The bonus to players is that they need only a single ID and they can gain access to dozens of games. They generally span many genres (action, FPS, sports, flash, board, and card games as examples).
Pmang is most notable for the game AVA, at least if the amount of advertising says anything about it. AVA is a first person shooter that uses the unreal 3 engine. I'll detail the sign up process for the site. I should note with almost every Korean website you visit, you'll almost always have to install an activeX control. Korean websites love activeX. I haven't run in to any problems with any of the ones I've installed. I can't guarantee that it will be the same for you, but with all my various software I've never had anything blow up or stop working.
The first thing you'll see on the front page is an orange button which has the word "신규회원가입" loosely translated it means we need to push this button to get started. Now you might think since you have a foreign social security number you could sign up as an adult on the site, later we'll encounter sites which allow us to do that, but this is not one of them. If you attempt to do this you'll encounter an issue where even though you can input a very long name, it will complain if the name is not in hangul. I'm not sure if this is an oversight on their part or what. First click the foreigner picture and move on to the agreement page. This is standard TOS stuff normal to any website. Check the two boxes and add the following word to your growing dictionary "확인" this is the Korean word that means "okay". The other word "취소" is one of many words used as a negative on these forms. While the first is fairly consistent the negative word seems to often change.
You will now be presented with a couple of boxes and some new words to jot down. The first word is "이름" it means name. In this case they're looking for your whole name as it would appear on your alien identification card. Type it in capitals and don't leave anything out. It will just slow down the registration process. Next is your birthday in YYMMDD format. The next is your gender. "남" means male and "여" means female. Also handy if you find yourself in front of a pair of bathrooms that don't have pictures on them. Click okay and you'll be presented with another box. They're asking you for a 4 digit number. This will become your ID number. Write down the whole string starting with your birthday and hit okay.
Now we're on to the main registration form. There are some keywords and items here. "아이디" as it sounds is "ID", "닉네임" means nickname. "비밀번호" means password. The one below that means repeat your password. "비밀번호 찾기 질문" means secret question. "이메일" means email. "주소" means city. "전화번호" means cell phone number.
These are fairly explanatory. First upon clicking the ID field a pop up will appear asking you to choose an ID. It will first confirm availability. You can only use english letters and numbers in this ID. The nickname allows you to use hangul if you so wish. The password can be 6-32 characters, including english letters, numbers and special characters. I believe it must contain one letter and one number. For the secret question just choose a random option from the list and type something as an answer. Write it down just in case you ever lose your password and what to try and recover it. For the email you can choose one of the main korean email providers or choose the last item on the list to use your own email address (like hotmail, etc). Uncheck the box if you don't want spam. In the cell phone area choose your provider and input your number. This can be used to recover your password as well. Uncheck the box to avoid sms spam. The last field is an image of your ID. Take your alien registration card, get a nice scan of it (or a really clear picture) and attach the image to the form. Hit okay. Usually within a day they will approve your account and you're good to go. You will have successfully signed up for your first Korean game portal.