Installing opencart to the subdomain of an existing website

Hello;
I have an already working website originally created with mobirise; i would like to install opencart in a subdomain and use it to create a "new site" to use as a store and run in parallel with the old one. The website is hosted by Ipage.
I assume is possible but how should i go about it? I don't want to compromise my already existing website.
Thanks

Depends.
You can use Softaculous Installer from you hosting Control Panel, by chose different folder.

Ex: you_store_url/store_demo

Or you can create in public_html a folder (my_demo_store), upload opencart version. Create another database from cpanel hosting, then install manualy from a browser

you_store_url/my_demo_store

I personally would rebuild your Mobirise site in Opencart as you will then have one seamless site. If you use a decent theme it would be pretty straightforward.