Don't "go to edit the site"; that's
supposed to take you to the File Manager (where you can, you know, edit your site, as opposed to manage your account/install scripts/etc.). Just go to
https://x10hosting.com/sso/login/ and log in; that will take you to cPanel (perhaps to the custom "Basic" theme, which is dumbed-down a bit for non-technical users). You should be able to get to Softaculous from there. If you're familiar with cPanel, you may want to switch to the x3 theme. There should be a "switch theme" option on the page, but it may not work (it doesn't always, and sometimes staff has to make the change happen). If you can't switch cPanel themes successfully yourself, post back in this forum to have a staff member help you.