How can I configure my ipad and iphone to use iMessage?

Settings>Messages>Send & Receive at>You can be reached by iMessages at. You must select the same phone number or email addresses on both devices to use as your "contact at" address for Messages.

if you want to link your iPhone number to use for both devices, take a look at this.

http://support.apple.com/kb/HT5538

Here are some instructions:

http://support.apple.com/kb/HT3529

more info is required

is your problem setting imessage up?

is your problem setting imessage up when it's on more then 1 device?

is your problem sending imessages from iphone to ipad?

is your problem making sure that all messages goes to both devices?