add this line of code
<img src="<?php bloginfo('template_directory')?>/images/yourlogo" />
if you want to add some css styling to it
<img src="<?php bloginfo('template_directory')?>/images/yourlogo" class="logo_css" />
Simply increase the memory allocated to php, note that many hosts set the PHP limit at 8MB.
Contact your host & Increase PHP Memory to 64MB
define( ‘WP_MEMORY_LIMIT’, ’64M’ );
or higher
If you are trying to install in your local computer just edit the php.ini file
memory_limit= ‘8M’
change it to something higher value problem should be solved!