Screwed up bigtime
MediaWiki usernames always must start with an uppercase letter. So the user account, which siteground created for you is invalid. Ask them to create another user with the first letter in uppercase.
Another possibility would be to go through the installer again and have it create another user for you.
88. Thank you for your help. I did go to Softaculus and uninstalled and did a reinstall and got a new name and password. I hardly knew what I was doing but it did work out ok. Actually talking to siteground is not that easy, lol, despite shelling out extra for "premium support." Apparently it only deals with issues relating to the host, not software support. But that did work. Thanks again!