When you import an installation to Softaculous it will just update the Softaculous records with the installation details (URL, path, database details, etc) i.e. there is an installation.
So when you want to upgrade to backup your installation Softaculous has the details required to perform that action.
Also when you import an installation it will not make any changes to your installation. It will just update Softaculous files with the installation details.
If your installation is in the "public_html" directory you have to leave the "Directory" field blank. If you had your installation in "public_html/mysite" directory for example in that case you would have to fill the "Directory" field as "mysite".