To add a link to the collection you need to click button "collection" under 1st post of a necessary topic and choose yuor some collection. To create some collection you need visit "Collection" tab at the top of the website and there choose "Create collection" or "My collections".
I understand the process, as I have two collections in which I save the charts I want to get. I no longer get the option of saving to either of my collections any more. Only a box that says Collection with an "x" to close is shown.