BackWPup wont install

I am trying to install BackWPup as I have never backed up my website after having it for a year. I’ve tried to install it using the ‘add new plugin’ but when I click install, I get this message:

Downloading install package from http://downloads.wordpress.org/plugin/backwpup.3.0.12.zip…

Unpacking the package…

Fatal error: Allowed memory size of 67108864 bytes exhausted (tried to allocate 19013 bytes) in /var/www/vhosts/greengirlstuff.co.nz/httpdocs/wp-admin/includes/class-pclzip.php on line 4215

I had a similar problem when trying to install woocommerce and eventually gave up and just used wp-ecommerce instead.

I also had a similar problem when trying to upgrade to wordpress 3.6 except it stopped at ‘unpacking the package’. I will deal with that after I’ve got the backup sorted out. For now, can someone please help me with installing the backup plugin? Thanks