Note that you may receive a file corruption error if when downloading the Noteworthy Composer file you choose "open this file from its current location." Therefore choose "save this file to disk." If for some reason that doesn't work, then just downlad the zip file at the top of the page you're interested in.
For indications of performance difficulty, the grading system is according to the Associated Board (UK) system. It runs grade 1 (beginner) to 8, where 8 is generally considered pretty good by most amateurs. A good grade 8 mark is the usual qualification required to study an instrument at a UK university for a music degree.
All these can be simply listened to as Midi files. However, if you'd like to see the music scroll by as it plays then download Noteworthy Player (Freeware - Hooray!) You will then need to download the Noteworthy composer file and drag it into the Noteworthy player window. Then click on the "play" button and it will all happen.
Note that the pieces could sound odd if you have a very different sound card than the one I wrote them for. If you have a lesser sound card than a sound blaster then the pieces might sound better in the alternative version available at the top of each page.
You can just drag the midi file into Noteworthy player but I wouldn't advise that as it may look a bit weird, depending on the exact layout of the music. Also, not all the subtleties in the noteworthy composer file will be shown. For instance the rhythm is approximated and if I change clef or span too large a range on the same stave then you will get extra staves which might look a bit loony. So I advise downloading the Noteworthy composer file unless you are in a terrible hurry!
To obtain a printed copy and to print out and transpose individual parts you will need Noteworthy composer which is available as shareware. Last time I looked, (and I have checked this with Noteworthy Composer technical support) the shareware version would give you printouts but will not allow you to save any changes you make to files from a registered user. Noteworthy Composer is not very expensive to buy anyway (I don't work for them - honest). For everything a user of Noteworthy Composer could wish to know see the NoteWorthy Composer Scriptorium.
You are free to distribute and use the music as you like, but I would appreciate an if you use any of my music, just so I know what the punters like (and to help my ego...). Or better still sign my "dreambook" and rave on about what a great site this is for all to see!