Ok. Make sure the folders are actually on the server, not the computer. If you are using a computer email program you can have both local and server folders. Only server folders are synced to all devices. The best way to check this is to access your email via the website browser, if you have one. If the folders are not on the website, you can't sync them to the iPad.
You should set up any mail programs on your computer with the same IMAP server, to keep things simple; if you haven't already done so. Otherwise it too may not see the server side folders. Once you've done this, make sure you know what folders are local and which are on the server, and use them accordingly.
In the computer's email options, you should also (when IMAP is set up) have the option of having your Trash, Sent, and other default folders on the computer or the server. Choose the server for maximum portabiltiy. You may also find these settings in the account settings for the iPad. You'll probably have to dig for them.
Once folders are on the server, they should sync automatically. You may note see them on the iPad if you have an inbox selected for viewing. Tap on the MailBox button at the top left of the email list. (it might say something else). Keep tapping on it until you see a list of inboxes and accounts. With the account selected you can move back and forth through your folder files the usual way.
There is a settings that tells each folder how many emails max to load. If you have more, scroll to the bottom of the email list for a Load More Messages option.
Ok, hopefully one of those things helped. If not, give me some details of what you see when try to do them, and maybe I can make another guess.
