Welcome to the iPad Forum. Hope you enjoy your stay.
Are you using the app, or the website? If using the app, new threads are started by navigating to the forum of your choice, hitting the action button (top right of screen) and selecting New Thread from the drop down menu.
If you want to check before posting a new thread, just do a simple search using the search facility at the bottom of the screen.
Don't worry too much about covering old ground. If the iPad is new to you and a question was asked and answered a year ago, we don't expect you to go trawling through thousands of old posts. Better to ask and get new answers from active members.