Picaxe Sertxd

I recently was given an irobot create and I am having trouble with coding it to send the specific commans via Sertxd

Details

This is a iRobot create with a picaxe onboard? You have a picaxe and you want it to talk to a iRobot? You are trying to get a picaxe to talk to a computer or computer to picaxe? What pins are you using? Is it an inverted tx problem? What is a “command”? How is it wired?

More please.