I love walk designer and wish that Carrara had it.

However, if you are going to be using Carrara for the animation, actually creating the walk cycle in Carrara will provide you with more flexibility during the animation process because every element of the figure is key framed when imported from Poser. This means animating other parts of the body or using Carrara's animation clips won't really work.

That said, there are two ways. 1) create the animation in Poser and import the Poser file into Carrara, 2) create the animation in Poser and export a .bvh motion file which you can import into Carrara and attach it to the figure of your choice. 

I recently completed a walk cycle tutorial for 3D World Magazine using Carrara. I'll get it post up in a little while so you can take a look. The tutorial is for creating a cycle for a spider but the same tricks can be used for a person.

Mark