Blue and red wires come from under the flywheel. Where to attach which?

Hi,
Generally the red wire is the positive 12V DC source for charging the battery. This is not hard-and-fast, but is close to an industry standard.
You can take the link below:
http://www.smallenginesuppliers.com/html/engine-specs/briggs/Briggs_alternator_replacement_guide.pdf
Peace,
Clarke