Adding things to Content Center

Folks,

About a year ago I managed to do a test in which I loaded a T-slot template to the Content Center and was then able to use us it in Frame Generator and had the “Insert Frame” command replace my 3D lines with tslot. A little mitering of corners and extensions and voila…robot chassis done.
Since I loaded AIP 2014…the template seems to have vanished and I can’t remember how I got it in there in the first place.
I know I was guided by a “Nate the Intern” video…but I can’t find that as well.
I’d appreciate some help if anyone is familar with my situation.
Doc