Cannot log-in after install–with error message: “Cannot modify header info.”

I thought I got through all the steps in the “Famous 5-Minute Install.” Indeed, my WordPress site appears to be up and running at
https://s213242494.onlinehome.us/MyAACPS/?page_id=2. (I use 1and1.com for my webhosting and that ugly URL is the default one 1and1.com allocated me pending my selection of a better domain name). However, when I log in to my site I get the following error message consisting of six warnings, each with the same basic type of error:

• Warning: Cannot modify header information – headers already sent by (output started at /homepages/6/d213242484/htdocs/MyAACPS/wp-config.php:1) in /homepages/6/d213242484/htdocs/MyAACPS/wp-login.php on line 260

  Warning: Cannot modify header information – headers already sent by (output started at /homepages/6/d213242484/htdocs/MyAACPS/wp-config.php:1) in /homepages/6/d213242484/htdocs/MyAACPS/wp-login.php on line 272

  Warning: Cannot modify header information – headers already sent by (output started at /homepages/6/d213242484/htdocs/MyAACPS/wp-config.php:1) in /homepages/6/d213242484/htdocs/MyAACPS/wp-includes/pluggable.php on line 595

  Warning: Cannot modify header information – headers already sent by (output started at /homepages/6/d213242484/htdocs/MyAACPS/wp-config.php:1) in /homepages/6/d213242484/htdocs/MyAACPS/wp-includes/pluggable.php on line 596

  Warning: Cannot modify header information – headers already sent by (output started at /homepages/6/d213242484/htdocs/MyAACPS/wp-config.php:1) in /homepages/6/d213242484/htdocs/MyAACPS/wp-includes/pluggable.php on line 597

  Warning: Cannot modify header information – headers already sent by (output started at /homepages/6/d213242484/htdocs/MyAACPS/wp-config.php:1) in /homepages/6/d213242484/htdocs/MyAACPS/wp-includes/pluggable.php on line 770

I have no idea how to interpret this error message. The practical result is that I cannot log in to my WordPress site. Any thoughts on how I might gain access to my site (or even just interpret this error message) would be much appreciated.