Can't get to admin screen/dashboard

I just installed WordPress in order to create a site for a client, this is my first time installing WordPress for this purpose.

Everything seemed to work out fine when installing and I can log into the site, but when I do all that comes up is:

Warning: Cannot modify header information – headers already sent by (output started at /home/content/11/8863111/html/IIP/wordpress/wp-config.php:4) in /home/content/11/8863111/html/IIP/wordpress/wp-login.php on line 362

Warning: Cannot modify header information – headers already sent by (output started at /home/content/11/8863111/html/IIP/wordpress/wp-config.php:4) in /home/content/11/8863111/html/IIP/wordpress/wp-login.php on line 374

Warning: Cannot modify header information – headers already sent by (output started at /home/content/11/8863111/html/IIP/wordpress/wp-config.php:4) in /home/content/11/8863111/html/IIP/wordpress/wp-includes/pluggable.php on line 680

Warning: Cannot modify header information – headers already sent by (output started at /home/content/11/8863111/html/IIP/wordpress/wp-config.php:4) in /home/content/11/8863111/html/IIP/wordpress/wp-includes/pluggable.php on line 681

Warning: Cannot modify header information – headers already sent by (output started at /home/content/11/8863111/html/IIP/wordpress/wp-config.php:4) in /home/content/11/8863111/html/IIP/wordpress/wp-includes/pluggable.php on line 682

Warning: Cannot modify header information – headers already sent by (output started at /home/content/11/8863111/html/IIP/wordpress/wp-config.php:4) in /home/content/11/8863111/html/IIP/wordpress/wp-includes/pluggable.php on line 881

But I can access the site fine (https://sineadmcelhone.com/IIP/wordpress/), just can’t get in to make any changes. Please tell me what I am doing wrong and how I can fix this please!!