My lack of experience of Joomla means I have no idea where module 7 position is.
"Position 7" is referring to the Joomla default template, Protostar. Obviously, you are using a different template, so the module is unlikely to show. You'll need to select a module position of your template, and for starters you should click on the position selector and pick a position listed under your template. It would certainly also help if you had a "map" of your template's positions - best ask whoever has made your template.
To give it a try, you may try to find and select a sidebar position, e.g. the same as the one which your category menu is published to - might be something with "left".
In any case, this is standard Joomla functionality and procedure, not related to HikaShop but valid for all modules on your site. In other words, you should maybe make yourself more familiar with Joomla and its basics. There are a lot of tutorials out there on the web.
When I add to the cart according to the buttons I see no change ...
As already pointed out, the configuration as described here
www.hikashop.com/support/support/documen...onfig.html#main_cart
gives you options for action after something has been added to the cart, e.g. to show a popup message. Why not try that?