Each time you load a page, the linker will look for things in posts that look like scripture references, and if it finds any, will add a link to them that pops up an embedded version of the text on Sefaria with a Read More link to go to the full thing. This is also why you'll also see a short delay before these links are added sometimes.
This also means that pages on this site should gradually start to be listed on Sefaria as having linked to specific bits of scripture.
Since it's not always clear exactly what text will generate a link to Sefaria and what won't, there's also a second new button (the Torah scroll icon). While you're writing a post, you can select some text that you think might be a reference and click the button - it will bring up a list of suggestions that will generate Sefaria links, and clicking on one will replace your selected text with that reference.