There are different ways to do it. In this case "signet", the plugin of Dashub to be plugged in to your web browser, isn't installed.
First: posts on Facebook can be either private or public. This technique won't work with private posts. You can save posts that have been shared through a Facebook page or have been marked as "public" by the author.
copy the url (the address) of the page you wish to save.
There are different ways to add an item. Inside your Dashub, click on the "Private deck" tab. Click on the plus sign to add your link into the corresponding folder.
Or you can click on the folder title. Inside the folder, click on the plus sign (top right).
Write here your content
When you click on the plus signe. A box will appear.
Paste the url (the address) of the web page
Check if the folder is ok on the left of Tag & Save. If it is ok, click on Tag & Save.
If the preview is a blank rectangle, it means that the post is private. It can't be shared. Don't forget to tag your item. It will ease your archive afterwards.
You can also subscribe to the source. the stream of posts from that page will be displayed into the selected channel.