Plugin instal error

After uploading plugin to ftp and acivatinf in wp admin panel i got this message and the site go's down! What should I do? Need help!

Fatal error: Allowed memory size of 41943040 bytes exhausted (tried to allocate 75 bytes) in /home/iconsul/public_html/masterminds-ec.com/wp-includes/post.php on line 595