Enable HTTPS
Click on the button to begin the conversion of your site's URLs to HTTPS.
The process itself will take about 5 minutes.
Note, however, that it might take up to 2 hours before your site uses HTTPS, as it takes some time to propagate to all nameservers around the world.
While you're waiting for the nameserver changes, read Converting to HTTPS, and Post-Conversion Tasks, which outlines what you'll need to do when the conversion process is finished (in 2 hours or so).