I’m not sure in there are special settings to enable, I don’t remember changing any flag.
in firefox open settings page, and in the text field at the top of the screen write “password”. among the hightlighted objects look for “saved logins” and click on it. in the top right corner click on the three dots and select “export logins”. this will create the csv file.
in brave open settings pag, then click on the lens in the top right corner, and write “password”. in the highlighted objects click on “password”. in the password section click on the first three dots (near the top of the page, and before the list of all passwords) and click “import”. this will import the file of the password from firefox.