TemplatesNext Toolkit

I have tried several time to install this plug-in (as recommended) but have been unable to do so. I receive the following error message:
Fatal error: Call to undefined function TGM_Bulk_Installer_Skin() in /home/content/p3pnexwpnas02_data02/70/2639270/html/wp-content/themes/i-max/inc/class-tgm-plugin-activation.php on line 1784