Menu on lefthand site

As an old Joomla user I am used to create a menu module to be used on the left (or right hand side for that matter) side of the page.
Now with Grav I am totally stuck.
I know I can build up a menu with pages but that only appears in the header of the page.

Anyone to help me out here?

I have noticed that in the template I am using ((Helium) there is only a horizontal menu configurable. May be that is my problem .....
Can somebody confirm that, please?

Grav doesn't really have this concept of 'modules' that Joomla does. The reason behind this is that working with distinct blocks is limiting, and Grav lets you display anything anywhere. Simply add the logic where you want it.

The menu in 'most' themes is displayed by just looping over the pages object from the Twig template. You can adapt this or loop over specific pages and output an unordered HTML list in a sidebar, then simply style it with CSS. The blog skeleton has a simple sidebar, if you look in the sidebar partial of the antimatter theme, you'll see twig logic there to output items for a menu.

This is pretty trivial if you poke around a theme, but it's not very well documented. I've made a note to add this to our cookbook section. https://learn.getgrav.org/cookbook