my story says to enter a design challenge
how do i do that?

Hi Jay and welcome to the forums.

The Story is referring to what are called Gem Events. Today at 1pm cst, you will see the large pink gem pop up on your screen in the upper left hand corner (it is always available to open just off the screen bottom left). Clicking pink gem that will open the Gem Event window. In that window is a Challenge tab. Today there will be a new Design Challenge for a room. Completing a room and submitting it will satisfy your Story requirement.

Good luck and let us know if you still have questions!