Trailing Slash Help Please

[brightgravity]

Hi I am setting up pumper sites, bought aged domains I have installed WP but can't figure out how to get the trailing slashes to show on the URL, does anyone know? Tried everything possible in the 'general' and 'permalink' categories in 'Settings' in WP but can't work out how to do it?

Aware that I need the URLs exactly the same in order to get all the link juice.

Thanks!