Sorry about that, the url is wrong. That is a dev environment we use. Please change "http://pmsp2013cpdev1.cld.sr/sites/codeplex-foundation
" to the url/path to your
Or better yet, navigation to the Design Manager (found in the Settings dropdown) and then click on 6. Edit Page Layouts. Now click on the page layout you wish to modify. This page layout will load in the Page Layout Previewer. You will find the proper link
to your Snippet Gallery in the upper right corner of the page layout preview.
I suggest using the link to the Snippet Gallery from the particular page layout you are going to edit because then the "Page Fields" snippets will actually list the content type columns available to that particular page layout.