You can find threads that you have posted in by going to the upper right side of the screen and clicking "search" from the gold menu bar. When the search window opens, you can use the "search by author" bar and type in your user name. This will bring up all threads you have posted in with the most recent first. If cookies are enabled, it will also show a Yellow highlighted circle to let you know there has been a new post on this thread since the last time you viewed it.
To go to your profile, you can also click on "my models" from the blue menu bar at the very top of the screen. From your profile, you can select which forums you want or don't want to show up when you click on "my forums" . For instance, I have no interest at this time in boats, rockets, tanks, etc. so I don't want these forums showing up in "my forums". If for some reason I do want to see a forum that I have not selected, I click on "discussion forums" which brings up all of the forums. Hope this helps, just keep asking questions and check the thread periodically and someone will eventually come up with the answer you need!