Magento 2 installation of theme

I hope someone can help me. I’ve just begun creating an ecommerce site with magento 2 which i am using through Builderall. This here is the isssue, i do not have access to a cpanel and can’t ftp into the site. I would like to purchase a theme from you but have no idea how to get it into the system. It appears that you are not connected to the magento marketplace which I am able to click on items which get installed “by magic”.

Any ideas for me?

Thanks in advance