To increase the php memory used by wordpress:
- Option 1: download your wp-config.php via FTP, open with a text editor and add the following lines below the WP_DEBUG value as shown here.
- Option 2: Login to your Hosting account as explained in Hosting Account Access and navigate to the "Files" tab. Click on the httpdocs folder or the domain name in question within File Manager as shown here.
Navigate to the root of your Wordpress installation and click the small arrow that appears when hovering over the wp-config.php file and choose "Edit in Text Editor" as shown here. Then add or change the WP_MEMORY_LIMIT as shown here. Make sure to click/select the "Save" button at the bottom of the editing form.
** Remember to turn off debug mode by setting this to false after your troubleshooting as non-fatal errors may display on the screen/site.
You can find the full documentation on Wordpress wp-config.php at https://codex.wordpress.org/Editing_wp-config.php#Increasing_memory_allocated_to_PHP