so i have a airport extreme plus an express that i have never used, i would like to set it up but not exactly sure how
i would really like to know why i cannot connect the express to a already existing extreme
Unfortunately, your post does not provide much in the way of basic information at all. Things like.....
Which model of AirPort Extreme do you have?
Which model of AirPort Express do you have?
Are you trying to connect the AirPort Express to the AirPort Extreme using wireless?
Are you trying to connect the AirPort Express to the AirPort Extreme using a wired Ethernet connection?
What operating system are you using on your Mac or PC?
If you have tried to set up the AirPort Express, what error messages did you see?
If we could get more details from you, we might be able to help.