If you want to build the one in the supplied schematic I suggest start by reading the datasheet of the fingerprint verification module that they are using:
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If you have never written code for a 8051 - start by buying a small development kit and play your way around from there upwards using the tutorials.
I strongly recommend buying the one from the site where you got the schematic from:
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For learning programming the 8051 this would be an excellent resource:
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