I can teach you the basics right now, if you want.
To access the main part of the forum, just click the bold 'POKECOMMUNITY' at the top, it may be different depending on the style you choose, so to access the style, just click on the User CP and go on Forum Styles. Go on Quick Links then Open Contacts Pop-up to see who is online, AKA, me. :P Customize Profile basically means change your profile colors, since yours are currently default. Maybe go for some reds, greens, oranges, purples, whatever you like. :D
For your profile picture, have anything, but it must be a certain size, so when you go on your Profile Picture options, read the little writing under the 'Choose File'. Need anything else, just ask. ^^
Oh yeah, you have to post in the Forum a few times or you could get banned. Just post in some of my threads to be on the safe side, if you wish. To find out what I made, go on my Statistics and click on 'All threads started my Gym Leader Rozu.'
Maybe you'll meet Nate, otherwise JNathan. <3 (he knows I have a crush on him and he's crushing on me too! Too stalk our conversation, just click on 'View Conversation' between me and him. :P