At the bottom of that page is a rectangle with a link to (currently) Timbres Of Heaven GM_GS_XG_SFX V 3.4 Final.7z
Click it to end up on this google drive page. On the top right you can click the downwards pointing arrow to start the download. It'll take you to this page: https://drive.google.com/uc?id=0B2NEzl-56UFHd054VnJETzJOZjg&export=down… where you'll have to click the Download anyway button.

7zx Mac Download Software

File extension(s) MIME type Official name Platform Description.bz2 application/x-bzip2 bzip2: Unix-like An open source, patent- and royalty-free compression format.The compression algorithm is a Burrows-Wheeler transform followed by a move-to-front transform and finally Huffman coding. File extension(s) MIME type Official name Platform Description.bz2 application/x-bzip2 bzip2: Unix-like An open source, patent- and royalty-free compression format.The compression algorithm is a Burrows-Wheeler transform followed by a move-to-front transform and finally Huffman coding.

7zx Mac Download Torrent

This gives you a 7zip archive of the soundfont, to extract it you'll need a program such as 7-zip (free, https://www.7-zip.org/ ). After installing 7-zip, double click the downloaded file, then in 7-zip highlight the .sf2 file in the listing and press the Extract button
After extracting it, you should be able to double-click that sf2 file to start the process of adding it to MuseScore (see https://musescore.org/en/handbook/soundfonts-and-sfz-files#install )