You will need David Pilling's !SparkPlug to de-archive the software contained here. Luckily, I have it here for you in a self extracting archive. All you do is download the archive, set the filetype to &FF8 (Absolute) and run it as you would a normal application.
Incase you have problems, I've a help page for you.
BBC B software
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Help with de-archiving the self extracting archive