File Manager and FTP
I’m going to presume you are using SiteGround for the rest of this section. I know there are many others out there but I’ve used many of them (even the big names) and they all fell down either with support, moving websites, or technical issues.
Under the ‘Site’ tab of your dashboard, you can configure FTP, use file manager or configure your databases. FTP can upload and download large files securely. Your web designer may ask for access and in some circumstances, you may need to use it to install the software.
File Manager will let you view, add and delete files to your website.
Read the SiteGround FTP notes here.