memory problem

I can’t access my dashboard since I got this messageFatal error: Allowed memory size of 41943040 bytes exhausted (tried to allocate 7680 bytes) in /home/robertma/public_html/blog/wp-admin/includes/class-wp-list-table.php on line 180

I read the documentation but did not find where I can change the memory size php.
Looked into wp-config, wp-settings.php and some other places did not find anything.
Sorry for my english, can someone help me? Thanks