HTML novice who just started using Altervista, how do I modify index.html?

I get the following message:

File index.html has not been saved. Check file permissions or those of its folder.

I can upload my own HTML and edit those files, but how do I edit the index file? How do I change the default page "poetryrocksalot.altervista.org" to my own html page?

[Gianluca]

I happpens because your file permissions on index.html are wrong, the issue has been resolved now but you should check your client FTP in order to avoid this in the future. You should disable the "preserve permission" feature if your client supports it.

Alright, thanks. Is an FTP client recommended or necessary for altervista web hosting? Should install FileZilla client or FileZilla server? I've only experienced using an ftc client to access a university's files, so I am unsure what is the next step.

[Gianluca]

There isn't any recommended or necessary client, every client should be fine, Filezilla is probably the most used