I put a link in my own profile. The syntax is explained here: http://www.wikitree.com/wiki/Free-Space_Profile
I have also created a free space profile that is a directory to all my free space profiles. I then put a link to this directory in my profile.
I put links to my free space profiles into the profiles I create/edit. To make this easy, I put the Wiki syntax for all my free space profiles into one simple text file on my computer. I can do a search in the text file for the needed free space profile, and then copy-and-paste the correct syntax into the profile I am working on.