Trying to find the right file to add / edit your latest Magento e-commerce website?
Login as Admin, go System > Configuration
Top left you see ‘Current Configuration Scope’ – choose ‘Main Website’ assuming you have a default installation.
Then scroll down on the left till you see ‘Developer’ – hit that.
Then open the panel in the content area that says ‘Debug’ and set Template Path Hints to ‘yes’ (Block Names also if you want them)
Save and done.
Credit to Magento Community guy stevewar for the video here