If you want to manually Sync your site, you can do so through your site's dashboard. To do this, you'll first go to the Settings menu and click iThemes Sync.
This opens a screen where you will enter your iThemes username and password then click Sync.
Now you'll see the iThemes Sync page where you can either click the Go Manage Your Sites button or add additional users. Adding additional users is helpful if more than one person will be managing updates for this site.