General settings can be found under (design > theme editor):
Choose 'general settings'
Custom Shopping cart
Activate the custom shopping cart page here. When this option is disabled, Lightspeed's default shopping cart page will appear.
Activate the custom blog page here. When this option is disabled, Lightspeed's default blog will appear.
Google Tag Manager
Insert your Google Tag manager code here (f.e. GTM-XXXXXXX).