Please follow these step to add the menu in sidebar :-
Open TemplateToaster > General > Sidebars > Add sidebar to your template > Export your template.
Open Joomla backend > Extension > Install your exported Template.
To make the template default for all the pages of your site go to Extension > Templates > Styles > Choose your exported template.
To add the sidebar menu click on > Extension > Module > Click on the menu or items from list that you want to add in sidebar >
Choose the Position for your menu Left[left] > Save.
Check site frontend your menu has been placed in left sidebar.
If still, your issue is not solved please open the support ticket at: https://templatetoaster.com/support/
and attach the screenshots of the issues.