You can link to other datacards or pages in your Silk in various ways.
In a text block, you can select some text and hit the link button in the toolbar. Type the first few letters of the datacard or page you want to link to, and Silk will suggest the datacard or page for you.
You can also link to datacards and pages from the Fact Sheet. This works by entering a value with the same name as a datacard or page.