The BPM or tempo is set at the top-left of the first page of the score, which is done by clicking on the default number (which is "90" on the Mac) and then changing it to whatever BPM or tempo you want . . .
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NOTE: The BPM or tempo indicator has a quarter note, an equal sign, and then a numeric value, so it does not actually say "BPM" or "tempo", but this is the way it works, since a quarter note is one beat in the default 4/4 time signature, which maps to 4 beats per measure with a quarter note being one beat, and "BPM" is "beats per minute", which is somewhat but not entirely intuitive. However, it is important to consider the time signature, because for example 6/8 maps to 6 beats per measure but an eighth note being one beat, which probably changes everything, except that I do everything 4/4, based on the general view gleaned from Joseph Schillinger's System of Musical Composition (SoMC) that measures nearly never are correct in classical and what now is modern music, where the primary purpose of the measures is to provide a reference point for musicians in the sense of "everybody look a measure 22, where we will begin playing, hopefully this time in the correct key" or whatever . . . ]
For example, as best as I can determine the European Single of "Who Owns My Heart" (Miley Cyrus) is 136 beats per minute (BPM), so if you set the quarter note value to 136 and then create a kick drum instrument that plays a series of quarter notes, you will hear that it is the same tempo or BPM as the Miley Cyrus song . . .
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NOTE: This is the YouTube music video for the European Single of "Who Owns My Heart" (Miley Cyrus), which is a stellar DISCO song . . . ]
http://www.youtube.com/watch?v=iVbQxC2c3-8There might be other ways to do it, but this is the way I do it . . .
If you search the Help file on "BPM", you will find more information on how to set it in different ways, although it appears to require a bit of reading, really . . .
Really!