File manager not showing up in "in browser editing"

Hi

I am developing a site inside Muse, and publish it to BC. I want it setup, so that the client can do basic editing, and this include uploading PDF's and link them on a page.

I found this in the help section on how to upload files to my BC site:

When I go to the site manager of my site, it looks like this:

I have tried two different BC sites, and no luck.

Could someone please tell me what I am doing wrong here?

Thanks in advance.

Ulf